@Sane Max – One of the things that I like about 6mm is that I prefer all (or most) of the bases to be the samer depth. I don’t think that I could fit chariots on 20mm deep bases, though.
This year, I re-based nearly all my 6mm ancients armies on to 60mm wide by 30mm deep bases. I am pleased with the results, although they need a slightly deeper battle field. The rules that I am participating in writing would normally want a 36″ deep board for 60mm wide bases, but because all the bases are 30mm deep, with careful deployment, you can get away with a 30″ deep board.
By the way, I tried Warmaster when it came out, and thought that it wasn’t bad as a fantasy game. I haven’t tried Warmaster Ancients, but suspect that there could be worse choices available. 
