>>19511404>Fire/Rock/Steel and Grass/Poison/GroundThese include the types you are trying to get rid of, so it invalidates the point of even doing so.
>Rock/Fighting/FlyingThe only problem is that rock is highly resistant to the moves which most pokemon and all starters have a lvl 5, scratch, tackle, etc. So its mildly unbalanced at the point in which you are trying to teach new players how the game works, ie if they pick the fighting starter it would need to have a fighting move at lvl 5 or the new player would probably lose, and rage quit, which is bad according to GF. Yes i know gen 6 did it, but every gen before that didnt, so who knows it giving the starter a STAB move will be permanent or not.