Yeah, I remember having trouble on Lunatic with Inigo's paralogue, although he did end up to be a god once I got him.
I was planning on passing down Veteran, because Veteran seemed to be on of the most useful skills in the game that you can easily get.
In my Lunatic run I did Sumia x Chrom and Cynthia was a god as a Paladin, literally destroying everything with Aether.
I did Nowi x Gregor in my Lunatic as well, and Nowi is just amazing in general, so I'm sure I'll be fine.
I've never tried using Miriel on Lunatic, because of how squishy she is and how much enemy phase matters in Lunatic, but I did use Lon Qu (who I married)
So if I really need a good magic user I'll consider LonQu!Laurent.
Thank you!