I never played like half of those maps so its hard to judge.

In case I don't vote here's what I think.

Remove:
1 Zm_wintercomplex_b1
2 Zm_vc2_citybrawl_b1
4 Zm_policeprision_fixed_rnk
5 Zm_freakhouse_v
9 Zm_roflicious_b1
20 Zm_aztec_ruins_v1

Maybe Remove:
3 Zm_bumfight_v2
6 Zm_siberia_v2

Leave:
8 Zm_ghs_abdandon_mall