Yeah, around here we regularly have Monotype Challenges where all of your battling pokémon must have a certain element (dual-types are your weapon against your chosen type's weaknesses. For example, if you do a Water monotype, you'll probably want Gyarados to shrug off Grass attacks and Quagsire, Swampert or Whiscash to nuke Electric-types.) Most participants in those just have three or four battlers, and then HMers. Your challenge is far more lax than we're used to, except that not only are you forbidding the trading of Starters, you're requiring us to make in-game use of a Legend. That'll confuse a few folks.