@csgt Regardless of what he actually does, Kevin still has those same powers. His power set still hasn't changed. Choosing not to use certain aspects of his powers for various reasons doesn't change his power set if Kevin is still able to use those very aspects of his powers...and he does. On occasion, unfortunately, but he still does absorb energy and mutate as a result of it. If a character can still perform certain abilities but doesn't actually use them most of the time, their power set is still the same because they can still perform these very abilities because their choice to use them or not is the only restriction (if you can even call it a restriction). If Kevin's mutation in Alien Force season 3 was say permanent, that would be a better example of an actual change in Kevin's powers/abilities. Kevin also does have a reason for not wanting to absorb large amounts of energy being that he doesn't want to mutate and thus be seen as a freak and he doesn't want to go insane, which not taking into account and context of Kevin in the Original Series, that does make sense. Kevin's power set in the sequel shows didn't change. What he actually does doesn't change what he's capable of doing.
Why the sequels did that? Because going alien was already Ben's thing, if they had kept Kevin using his powers like he did in the OS, it would be redudant and/or make Ben useless. So they used Kevin's powers in a completely different way.
Yeah, it's almost like Kevin isn't a good choice to transition into a more heroic character due to him being a proper and actual representation of Ben's true evil opposite as well as what you say in this very quote. I understand that they want to differentiate Kevin from Ben. To me at least, it just didn't work.
And no, using his own Omnitrix to take on different alien forms or create amalgamations is not the same as having the ability to absorb energy. The results are the same, or at least similar, but the process to achieve that result is very much different. In regards to Kevin as a character, having his own Omnitrix gives Kevin more control of his abilities, which doesn't fit in line with his mental instability and psychopathic nature...because it's the opposite of being controllable. In the Original Series, Kevin also stayed in his mutated state because of his powers. Kevin wasn't able to turn back to his normal self after he took on an amalgamated form. All that energy that Kevin absorbed stayed trapped inside of him and he wasn't able to expel it out. This further fueled Kevin's disillusions and instability, which is why Kevin blamed Ben even more for the very state that Kevin himself was in despite it really being Kevin's fault for it. Kevin having his own Omnitrix most likely doesn't provide that much complexity because, again, Kevin would have better control over it.
No, Kevin didn't do anything else with his energy absorbing abilities to present himself as a bigger threat to Ben...because he didn't have to...because he absorbed energy from the Omnitrix. He doesn't have to do anything different other than his mutation because his mutation already made him ideally powerful enough to present himself as a bigger threat to Ben and that's all thanks to his energy absorbing abilities.
Your example with Spider-Gwen is better. Granted though, that is in reference to Ultimate Spider-Man and the last time I checked, that show isn't really fond of by many due to there being many issues with the writing and storytelling and whatnot. I wouldn't be surprised if at least many or most fans and viewers took issue with Spider-Gwen having a high tech suit instead of having actual spider powers. Doesn't help Man of Action's case either since that they were involved with producing that show. Plus, Spider-Gwen's original powers were restored after that show ended. Gee, I wonder why? And yes, Sam Raimi's Spider-Man trilogy did portray Peter Parker shooting webs out of his wrist as opposed to him using web shooters. However, while it too is a better example to use (especially compared to your Quicksilver and Scarlet Witch example), it's also a much more minor example. In fact, it doesn't really change much about Peter's abilities. He just doesn't use web shooters. That's it. Pretty much everything else remained untouched as far as I know. Kevin on the other hand, we're talking about the possibility of him having all of his powers be removed and replaced by another Omnitrix. We're talking about changing one major aspect about Kevin that defines him and makes him who he is in favor of something that, to me at least, more likely doesn't fit Kevin as a character and possibly undermine him.
And sure, non-subtle opposites can work as long as the execution is done well. Never said that non-subtle opposites can't work. I just find that subtlety is better than having it shoved in your face. In regards to the Flash and what I'm guessing is Mr. Shazam, I don't think their opposites are as memorable. Usually, from my experience, when it comes to what is considered as the best and proper opposites to each other in the DC Universe, most people point their fingers at Batman and The Joker. Again, it's as if subtlety is better.
And yes, Man of Action can indeed find other reasons for Kevin to be bullied and to be rejected by his family and to keep his Original Series personality and whatnot. Would it have as much of an impact in the reboot as it did in the Original Series? I doubt it; especially considering how, as I stated before, Man of Action and the other reboot show writers undermined and screwed up almost every returning character in the reboot and how incompetent and lazy their writing often is. Here's the thing as well, my argument isn't about Kevin taking on alien forms and having an amalgamated form. I'm referring specifically to Kevin's original powers. I'm referring specifically to his ability to absorb energy because like I said before, that aspect about Kevin is such a major part of Kevin as a character. Again, Kevin's family rejected him because of his powers. Again, Kevin was bullied and seen as a freak because of his powers. Again, Kevin was mentally insane, mentally unstable, and psychopathic because of his powers. Again, his mutation and the further delusions that were created because of his mutation happened because of his powers. Almost, if not entirely, everything about Kevin pointed back to his powers. Kevin is a mutant. All these factors about Kevin in the OS makes him a walking doomsday scenario. A walking doomsday scenario who is obsessed with Ben and personally wants to make Ben suffer.
If Kevin had his own Omnitrix instead of having his powers, then he's not a mutant. He's not some hybrid. He's just a normal human boy with an alien watch. If Kevin is going to be bullied, it's most likely not going to be due to him being viewed as a freak. Kevin being rejected by his family wouldn't make as much sense because they too will most likely not view him as a freak. Kevin's Omnitrix is most likely not going to cause Kevin's mental condition to worsen and thus make him insane, unstable, delusional, uncontrollable, unpredictable, and psychopathic. Kevin is most likely not going to find himself stuck in some amalgamated form because of his Omnitrix and how it's better to control compared to his energy absorption powers. I have a feeling that Kevin is going to be set up more like Charmcaster in the reboot in regards to his quality as a character. Even if he does keep his original personality, it would more likely just not have as much of an impact and not have as much complexity, uniqueness, and subtlety to it with Kevin no longer having his energy absorbing powers in exchange for him having his own Omnitrix. That it would be set up in a more bland and generic way much like with Charmcaster in the reboot. You should know what I mean by that. After all, you did read my review of The Charm Offensive. I find that the reboot version of Kevin, much like with almost every other returning character, will just end up being a bland shell of his former self. Just the notion that Kevin is just a normal boy who also has his own Omnitrix already sounds bland and less interesting compared to his OS version. It makes him too similar to Ben and not as unique on his own. Again, take away Kevin's energy absorbing powers and you take away Kevin as a character. Kevin isn't Kevin without those very powers. I don't think Kevin having his own Omnitrix will be enough to salvage what is lost while also properly innovating Kevin as a character. It's a risk that I find is not worth taking. I could be wrong though but Man of Action and CN Studios' track record with the Ben 10 reboot already doesn't make things sound promising.