hi all.
after merging militia, I saved game & quit the game... go home... open & resume game again, and the merged "militia" slots were ready again for buying.
This did not work if I did not QUIT the game. I.e. JUST quick game & resume without closing game at all does not work the same way.
Well just advancing 1 turn a few more militia buildings, does not seem to me as a very gamey trick, but perhaps it should be solved...