Well Megatron I would be a bit more reasonable since even though the Decepticons are a large group they're usually isn't a huge amount on Earth if my Transformers knowledge is proper.

Really I'm wanting to keep it fairly loose, especially letting someone who doesn't live in the modern setting be edited to exist.  Like as an example setting the four nations of Avatar The Last Airbender as part of an island nation that exists in the current time, maybe with people aware of its existance or not.  Something like that.  If you want to tweak their story or personality they should still have what makes them special at their core.