I'd definitely focus on stages first, in that case. Better to have a solid game with 1-2 characters than a mediocre game with 3+; I think Sonic Team illustrated that for us quite clearly during 1999-2008.
Although, just played as Carol (the save transplant worked like a charm), and man, she is quite fun to play as. I love wall-jumping in games; so unrealistic, yet so cool. Mega Man X, Batman, Ninja Gaiden; love it all, and Carol here's no exception. I would like it if there were more cool goodies hidden up above for obsessive explorers like myself who climb tall walls for no good reason, though, or more overhangs/blockades to indicate that, no, there really isn't anything up there if you climb this wall, stop trying. I understand the stage was more designed for Lilac, of course, and that's fine, as per the first paragraph of this post, but if you ever get time...