Okay. I made Maribelle into a Valkyrie simply because of the added square of mobility she gets. I haven't gotten Lissa up to Level 10 yet, but when I do, I think I'll make her a War Monk.
Also, is it a bad idea to make Ricken into a Dark Knight? I mean, being a guy, I'd rather have him be able to use swords and tombs over staves and tombs. When I get another Master Seal on hand, I plan to make Miriel into a Sage. That way I still keep some diversity amongst my units.
I'm only up to chapter nine, by the way. I've been trying to get my guys up to levels slightly higher than I actually need them to be so I don't go getting killed again like I was early on in the game.