The problem I see with this is, unless how the boss scenario works is changed, you'd end up losing one or the other either way. And people wouldn't like that because then it would mean that they could only play as one character throughout the endgame, discouraging people from killing Vile Mark II. I'm not saying it's interesting, it kind of is, but the consequences of being forced to lose someone kinda sucks. Still, I think it'd be interesting to see both get their own, unique one-hit KO, although it'd sound broken. But that's up to Justin to decide, and I'm pretty sure he's done with working on the project, at least for now.
Yeah, it's also my understanding that Justin is done working on this project, and he has well earned his retirement, it's a great project.
But I wanted to ask since the lack of a one hit kill weapon for Zero is the biggest problem I have with the game. It makes the end game such a pain to slog through. And not because it's, hard, just boring. Also I'd like to point out that I'm speaking from a speedrunner's perspective, and we do runs of our speedgames hundreds of times over, sometimes thousands. So we complete the game several times per session usually. That's why a one hit KO weapon is a godsent, haha.
I don't really see a problem with being locked to using one character for the endgame since you would choose which one you use, and it'd be optional since you can always just skip Vile in the factory during the 8 mavs, and fight him in Doppler 2. But if you do sacrifice a character, the reward is the one hit KO weapon.
Also, in a speedrun, a one hit KO weapon isn't broken at all since in the speedrun of the vanilla X3, the saber rush is actually one of the trickiest parts of the run since it's not easy at all to get the quickest possible saber kills on all the bosses. It takes mastery to be able to use the saber efficiently.
Currently, in the Zero Project, to get a quick boss rush, I need to get the buster upgrade in Tiger, kill Vile, kill Zero in Doppler 2 and play the rest of the run as X. And also, because of that, I also need to get the boots because I need to do the Doppler 2 spike elevator skip, and it's incredibly hard without the boots.
I've personally never been a big fan of the boss rush in Mega Man games to begin with. You've already fought them once, so it's never been anything but boring to me have to go through all of them again. You're just using the same strats as you did the first time around anyway. Hardly exciting.
My favorite boss rush, however, by far is in vanilla X3 where you only have the saber and no buster upgrade; the saber has such easy, quick access without the buster upgrade, and it's actually pretty fun.
Here's the saber rush from the world record run by Luiz Miguel:https://www.twitch.tv/videos/256562253?t=00h32m18s
It's really cool.
So, yeah, the fact that this most fun part of the game (for me) isn't part of the Zero Project (as Zero) is a big bummer for me. :/