well you can add more then 11 buildings to your builder but there are only 11 squares in the order menu.
make different builders and switch them using a skill like metamorphosis.
I recommend you to think again does the game really need more than 11 buildings. Yes, it is possible to do that (as informed above) but the usability factor and the fun factor probably don't increase in the same relation.
Meaning: more buildings = harder to learn = harder to play ≠ more fun to play
my post was not an attack against you or something similar.
and anyways, its pretty hard to do it "better", your system has everything a map maker can wish for. its only a matter of taste what the better version is, which takes more time to create.
i myself made an own system long ago, well actually i prefer yours more then mine, the triggering of my version is much work.
Ghan has said he has fixed this. Monovertex please confirm this fix. This was only a problem with people that had signatures in the upper levels like not the special members but the respected members.