I hope you won't mind I will express my opinion too, even though I am not a V member, but I hope I can help a little
I strongly agree with kommando, dm7 is great and big enough map, 7++ is total crap compared to precision with which dm7 was designed.
Obviously too small map is cpm2, but that differs from point of view. For 4v4 it is a great nice map, but using all private slots it becomes much too crowded without even possibility to respawn. So during whole day it is perfect map, but in the evenings it becomes almost unplayable.
I would definitely keep 6++,dm7 and Overkill since they are generally accepted and we all like them i suppose.
Considering new maps or re-establishing old maps i suggest ospdm6 since it is big enough for higher amount of players. Then maybe ospdm11 could be nice from osp maps.
Last two maps are a bit different but maybe they could help to entertain in new ways and could bring certain pleasant changes. First one is Quatrix, dunno if somebody remembers, but it was played on Speedtek years ago and it's funny, dynamic map and big enough i suppose. And it makes you feel like Neo aswell
And last map I considered is japanctf though it is designed for ctf, but also it is a creative and dynamic map and really big, ideal for 6v6 or so. Nevertheless, I am not sure whether ctf maps are possible to put into rotation or maybe there could be some difficulties with the amount of powerups.