I've been chugging through Lunatic after poor EXP management caused me to hit a brick wall at Ch 17 (read; poor use of Frederick). I've beaten Ch 12 and am sitting on two Second Seals and was wondering which would be smarter to promote now rather than later. Chrom, Olivia, and Avatar are pretty well set so far (+Str -Skl Male Avatar married to Sumia who is just for pair-up bonuses and flight, Cavalier!Chrom to Olivia who I danced up to Lv 30 in her join chapter and SS'd to Dark Flier). My other pairs are Stahl+Miriel and Sully+Vaike, all still in their base classes but at or close to Lv 20.
One of my minor goals is to pass Wrath to Kjelle and one of the Troubadour/Valkyrie skills to Laurent. I guess Dual Support+, but who can forget the mighty Demoiselle or the absolutely broken Res+2? (Also passing Wrath to Cynthia and Morgan, but Avatar already has it as a comfortably leveled Berserker).
Jokes aside, the real question is would it be better to SS Vaike to Barbarian and then to Berserker -> Hero down the line (which is similar to what I'm doing with Avatar), or would he more appreciate the immediate boost from going straight to Hero and then going to Berserker later? In which case, I'd have a spare Second Seal to use on either Stahl or Sully (or Miriel, if I Rescue/Heal staff grind her next chapter and decided Demoiselle was good enough and I wanted her to go Dark Mage/Sorc long term)... but I'm not entirely sure if they would appreciate the promotion boosts more than a reclass, or even which of Paladin/GK is the better option for supporting/actual combat in this case.
...but man, I gotta say, once I got past the early chapters where everyone is terrible, I think Lunatic actually gets pretty interesting and fun!