Do you remember what made them overpowered, exactly?
I know there's people that focus on making as many Galeforce units, for example. So was it skill-based? Stat-based? Even if we can't get to the specifics in terms of skills and all that, we might be able to get started on the right path.
Me? I just want to make units that are annoying to deal with for people that street pass. Not so much looking to optimize, but still, annoying skills to deal with to at least provide some challenge.
I also forgot to pick up the easy to get boots in my last playthrough, and since we can only get two of those, I need to fix that. Ahhh...I wish I was playing right now. My playthroughs all eventually turn into a bit of a grind, but the look on my friends' faces is so worth it.