Yes we will need more. :p
However, me and Mika are the only current content developers because the game engine isn't complete yet so even if we got more content scripters/developers they had nothing to do at this point
Again, I don't know without knowing exactly how your system works (and to be honest, I'm not interested in finding out). I would guess that the metadata Players would only be used to set the player's trainer type, which means you would need one Player per trainer type.
Is there any reason why you're asking me about a system I don't know, rather than trying it out for yourself?