The general balances here IMO are to make decisions more collectively and more measuredly. If each person gets three nations, let another player ban one of the three. That cuts down on the worst cheese, even though you may end up with two tepid choices. If it's all from one pool, don't make it a free-for-all, make it a draft with random order. My preferred option is to combine these two: each player picks two nations from a reasonably large pool via a round-robin draft, then bans one of another player's nations. There's an argument in favor of doing the banning pass first and then letting the player pick from their two drafted nations. There's also one in favor of doing a first banning pass so the cheesiest cheese is rooted out ahead AND the remaining cheese being homogenized by a banning pass afterwards as well.
Players 1,2,3; Nations 1-30 -> [0,0,0];[1...30]
Player 1 bans Nation 6 -> [0,0,0];[1...5,7...30]
P2 bans N16 -> [0,0,0];[1...5,7...15,17...30]
P3 bans N26 -> [0,0,0];[1...5,7...15,17...25,27...30]
Random order of 3,1,2 is selected
P3 picks N1 -> [0,0,1];[2...5,7...15,17...25,27...30]
P1 picks N11 -> [11,0,1];[2...5,7...10,12...15,17...25,27...30]
P2 picks N21 -> [11,21,1];[2...5,7...10,12...15,17...20,22...25,27...30]
P2 picks N5 -> [11,21:5,1];[2...4,7...10,12...15,17...20,22...25,27...30]
P1 picks N15 -> [11:15,21:5,1];[2...4,7...10,12...14,17...20,22...25,27...30]
P3 picks N25 -> [11:15,21:5,1:25];[2...4,7...10,12...14,17...20,22...24,27...30]
(Either stop here and players pick which they want, or... every Player P now bans one of Player P-1's nations in any order)
P1 bans N25 -> [11:15,21:5,1]
P2 bans N11 -> [15,21:5,1]
P3 bans N21 -> [15,5,1]
The best solution for this IMO is to forbid/limit renaming unit types and then just make sure everyone has the original seeds and Advanced Description files. If you are renaming units, though, then agreeing ahead of time to always be unambiguously descritpive would be best, yes.