This idea is something that should be strongly thought about before made, it would be fun but if you had every region, all your pokemon would be level 100 by the second region or something which wouldn't be fun at that point. You could try adding the max level limit to 1000 solely for this game but that'd be just plain stupid. So maybe this wouldn't be the best idea. But if you don't care about any of that and want to play the rest of the regions with lvl 100s go ahead? o.o OR you could play the way Ash does and put all his OP Pokemon in the PC (like previously mentioned) So yup thats my opinion.