Curse is probably the only map that cannot be as the final map lol i would even put it in the beginning.
Liandri has to be in, the ultimate ut99 classic and its the perfect because it is hard to reach 200 (on 2v2v2v2) but possible for many top notch players.
Viridian is also a must...One of the most played maps and one of the most awesome as well...
Malevolence is a no go for me lol i remember playing it on 4v4 iTDM and it was already too much.
You can't really mess around the most played maps because they are just better for iTDM lol I'm sure there are possible best maps for KOTR (american ones like thursday and pahgio) but i can assure you 100% cluster maps like Malevolence (my fav 1v1 map) aren't. Just the time you lose waiting for the elevator will be the lulz
Anyway imo you can mess on the final map list but don't put the map that is the less loved in the ut99 community
I am pretty sure any other map (deck, liandri, stal, viridian) will be well received by most people.