I can just gen 40 nations at once and we go like... Jingo gets 1-5, racurtne gets 6-10, Moe gets 11-15, etc.
From a lot of testing...
About 1 in 3 nations are not complete garbage.
About 1 in 10 are decent to good.
About 1 in 25 are overpowered.
We can hedge a few things by imposing certain requirements on generation. Like, no sacred giants or zotz nations (often overpowered), or no hoburg, lizard, or goat-giant nations (usually underpowered).
We could also do something like a reverse draft so everyone is guaranteed to get a BAD nation.