Yeah, Gen 1 glitchmons are just a pain to work with. You're coding up tons of new moves, types, and effects, sprites are hard to come by, etc. etc. In addition, there's the nuance of glitchmons only being available in particular versions of the game. I think Gen 1 is officially considered to be played on International Yellow, which 'M doesn't exist in (hex 0x00 = 3trainerpoke and hex 0xFF = Q). Granted, it's not as if we're following that rule by supporting RB Missingno itself, which is RB only (there are 3 other fossil Missingno and Yellow's Missingno). There is also, to my knowledge, next to no research done with the vast majority of seemingly stable glitch moves. Obviously moves like Super Glitch or Cooltrainer, which are completely unstable and can wipe save files wouldn't be implemented (I joked with Kris that we should make them just delete all the user's teams). Generally speaking, though, the glitch moves are so underresearched in a link battle context that you're just making up effects. The scope of the project ended up being larger than Kris and I originally anticipated and so we have focused on implementing other things.
All that being said, there's no reason it can't be done, but I don't think adding one-off glitchmons is the play. I'll reject this suggestion for now, but not because it can't be done, but because if you're going to do glitchmon-related work you need to do more than one at a time.