Ugh you guys
Come on
You're gonna have to get permission to use people's shit (or even themselves) in your game. You've been told to ask about getting permission from people at least five times in this thread, when you shouldn't've had to been told once. If you're gonna inject people or blatantly steal their shit, you should probably make some effort to ask them about it. As of right now, I still haven't been asked if I want to be a player character in the game, though Saui did point to this thread earlier (but didn't say anything else). Truth be told, I don't care, do what you want -- it's not a big deal. The issue is that some people don't like being randomly chosen for shit they know nothing about. Just ask before you do, if you can.
Alright, second issue I have is this stage hierarchy. Aside from the blatant humiliation of being put on a stage "based on some guy's perception of my coding skill" (fuck man come on), you should at least honour somebody's request when they want to be on a certain stage. Forcing somebody to code for a stage they don't want to is not cool at all, especially when they volunteered to be in your project. At least make it look like you're not trying to blatantly blow them off.
"can i be stage one please?" "no wai man you're stage 10".
"I'd like to be stage 7 or 8 if possible" "you suck stage 2 for you"
Fucks sake.
An additional problem to throwing all of the inexperienced coders at the beginning is the fact that you'll have a bunch of supposedly "low quality" scripts starting off the game, with questionable balance and even more questionable entertainment value, whereas all the "good stuff" will be at the very end, and look significantly different from the start of the game. The balance, style, quality and entertainment value is going to vary so much in this project, and that's something to be concerned about, especially if you're forced to play them.
So, an easy solution to that, if you haven't considered it yet, is to not have unlockables. This makes it so you can play whatever, whenever, right from the start. At least then people can choose what they want to play, and wont feel like the game is progressively getting better or worse in quality/etc.. In addition to that, this also eliminates the need to have stages in number form, as well as the stupid hierarchy of "coding prowess". If possible, I'd recommend this. Otherwise, you might want to consider having people code whatever they want, and just systemmatically stick the cards in random places around the stages (based on their difficulty, I suppose, so at least all the easy-to-pass cards will be at the beginning), that way you'd have a good mix of coding styles and it wouldn't be so insulting to some of the more inexperienced coders who wish to join your project. As well, the less experienced coders wouldn't be forced to make shit-easy boring danmaku if they don't want to, since I'm sure they have great ideas for mid to upper difficulty danmaku.
Also, Johnny Walker, I love you so fucking hard, have my children.