Well, Drac, I agree with you about the thrill of coming back when the other team almost has you beat. Those games are absolutely awesome. You're almost ready to be out of spawns, hanging your head, and humbly typing "gg" in green, and then something happens. Suddenly, your team finally stages up. Somebody joins, or somebody quits, or you finally find the handle, or they go off somewhere to mess around, or they separate, and you're back in the game. That's happened to me a couple of times, and those are some of the most memorable games I've played. Especially when we didn't do it by suddenly outnumbering the other team or getting ringers halfway through the game.
As an aside: The PowerUpGrade idea would only be to modify Sudden Death, in games over an hour, where SD is over 10 minutes, and extendtime/reducetime votes begin to disrupt the gameplay. If you go destroy enemy stuff, you get cool toys. The carrot (not the stick) approach to anti-camp. (Also the "cut-that-out" approach to callvote/votebind abuse.)
But the overall idea of just randomly adding weapons or aliens or glowing power thingys has been discussed ad infinitum on the Mods page, and the general consensus is: Play the Game. Learn the Game. People worked on Play-Balancing the game. People are working on upgrading the game. If you think you need better/different weapons or buffed/nerfed aliens, you need to play more.
That being said, additional weapons and classes (as well as maps) are what many people expect with a "new" iteration. Gamers always say, "Wow! You're updating it? Can you add my latest half-baked kewl idea? Why not?". The same thing has happened with every game I've played, going back to Unreal1. Players say "C'mon, it would be kewl" and mods/devs/coders say "FDIY or stfu!". At least the Tremdevs listen to some suggestions. Didn't Norf get involved just by helping out?
My two cents.
PlayerOne has donned his Battlesuit
and awaits Flamethrower TK and Decon Base Nadespam