Both of you don’t really seem to understand the idea. You can already pick the civs random, full random and mirror. It will be another option that only affects your civ pick.
For example: you want to play an archer civ, bit you are fine with a lot of archer civs. So you select all archer civs and you let the game decided which archer civ you are going to play.
In the mean time you will still be able to pick you civ, if you like to pick a civ. No one will force players in using a semi random civ.
Currently you see in many tram games the same civs. Flanks go for archers, pockets for knights. As result you see the same civs over and over again. With this idea people can select a list of archer civs as flank and a list of knight civs as pocket. As result we will see more different civs in team games.