I think it would be extremely helpful to illustrate, on the region description "building", what "Greater Region" it is part of, namely because said regions are referenced in certain traits (like Roman Provincial Governor) and, most importantly, mercenary pools. Knowing which settlements encompass a region and which doesn't on only a look would be extremely helpful. Kinda like the green books from a certain other mod here.
Furthermore, how about adding some faction-exclusive pools to the mercs? That would be mighty helpful for factions that really need their mercs (namely, Gauls) but have to buy them before an invading army does (least this is the intention).