I'm also looking to experiment with a few new units on my 2nd run through. I've been looking at Etie/Amber reclassing into thief. I'm not entirely sure what the base stat formula is (based on character growths?) but they start with a lot of strength compared to their class bases and would have more strength in thief than Yunaka/Zelkov/Merrin at comparable levels (~3-5 point trade between strength and speed, some dex loss).
It might be fun considering daggers are really strong, a lot of units don't double anyway, and strength is more important when it comes to engage specials. Speed inheritance skills are also a lot cheaper point for point compared to Str/Magic.