I'm kinda concerned about that 3rd map that's "one map set aside".
Well just to leave some feedback there's info about elimination system:
AFAIR it was used in Starcraft II GSL Tourneys. There players competing in Bo3 (best of free - fight for two wins) were presented with map pool consisting of 7 maps. They were asked to eliminate two maps each they don't feel like playing. It's important to note they don't know each others' decision. After elimination, map pool got reduced from 7 to 3 maps (if elimination decisions overlapped, maps were taken off randomly).
+ both teams are guaranteed to learn those three maps good because their elimination choices mean they must prepare for 5 maps
+ it's guaranteed that there's no 3rd map that's biased towards any of the team (to some extent that is :->)
+ maps that are ridicolously biased towards one team are sure to be eliminated by their rivals (ofc if they are aware of it <-;)
I think that getting to choice favourite map will almost always lead to teams winning their chosen map and getting that random result from 3rd one. SS-dudes will get into tricky droplet fights, spinner-duded will get into 10 spinner maps, TAG4 dudes will go for the TAG4 maps, making their chosen maps easy for them and probably hard for rivals.