I'll contact with you if I feel my game get success.
But why VS doesn't make automatically OBB or external data files for accept google play? Many people wants put game into the Play Store with VS indie license as freeware and most of games are larger than 100MB.
I don't think Unity officially supports google play either. When I searched for what you were asking for, most of the results were about some third party tool for compiling unity games for google play. I guess it's not a standard practice (other than google play) that the games files need to be less than 100mb or whatever the limit is.