I plan on doing the same kind of thing on my playthrough. I haven't looked especially in-depth, but here are a few of the pairs that stood out to me:
Lazward x Hana: Great physical stats (R.I.P. Defense, though), and Samurai's a really nice supplement for Merc and Ninja. Lazward's other option is Orochi, which... eh? Maybe a Basara based on the hybrid stats, but lack of Lancefaire hurts (note that she can't even S rank Shinonome to get it)
Asama x Effie: Crazy high strength, nice speed, and the only negative stat is Magic. There's not a lot of inherent synergy between Priestess, Merchant, and Knight, but luckily Mitama can A+ with Soleil for Merc and (Female) Kanna for... well, whatever you want.
Benoit x Oboro: Very well rounded except for that crazy high Defense, and pretty much any kid will appreciate Lancer. I also much prefer Oboro with Benoit over Zero. I'm actually not a big fan of either of Zero's options; I'm thinking that I might end up copping out on the route-exclusive pair thing and marrying him to Felicia or something...
Odin x Orochi: Mostly for a Sorcerer with Tomefaire, but Orochi's nice Skill does help with Ophelia's inherent crittiness. This pair is actually somewhat limited class-wise, since Orochi's 3rd route A+ option gives her Dark Mage, and Odin's gives him nothing because he already has Samurai (That is how Buddy Seals work, right? I'm still not 100% sure on everything). That said, Odin's other 3rd-route option is Kagerou, which isn't necessarily bad but I think Kagerou's high strength is best utilized elsewhere.