Because of the limit of early game dragon pokémon I understand your Egg Group reasoning. However, I wouldn't make it a general rule - it's not what monotype is about, it would be monogroup or anything similar. There are more than enough Bug-types to be found throughout the game to not need Flygon or any other pokémon from the same Egg Group.
You can find a list of all pokemon per type you encounter on each route throughout the entire game. Feel free to use rotating teams!
Edit: Unless you feel uncomfortable making videos I would love you to make videos and put them on your YouTube channel - preferably with voice over. I will watch every single one
