Maybe you can make a little config or something for fav maps or best maps and bots will vote for those maps, if they are listed.
Even if it's randomized for the favorite maps it's mostlikly going to choose one of them.
I don't think having 4 fav maps or even 3 in 1 vote session is impossible.
Like
pb fav_maps "
cs_militia
de_dust2
de_dust2_1337
de_dust
de_rats
fy_repub"
The chances that all of those maps in 1 vote session is small
But my logic is very small in bot coding so I don't really have a clue