Hey SWC, ok so I just wanted to add a little information to this subject as I fear your max skill calculations are either incorrect or perhaps not a constant? Here's why:
I'm looking at Forgrimm now. If you start a Dwarf Mercenary and reduce all of their weapons stats as low as possible as you suggested to see the bonuses, his skill with 1 hand axe/mace is 6, and with 2 hand axe/mace is only 2.
According to your formula, at level 4 his maximum skill with 1 hand axe/mace should be 13 (which it is), but his maximum skill level with 2 hand axe/mace should only be 9. However, his 2 hand axe/mace skill at level 4 maxxes out at skill level 12... only one point below the 1 handers. Soooo...now I have to wonder what, if any, the formula is.
I know I am obsessing over numbers, but I'd really like to know what skills to invest points in, especially in my fighters! I'm going to go ahead and keep Forgrimm's 2 hand axe/mace maxxed out because 1 point less maximum is very little, and I felt like making him a 2 hand fighter. I know some people out there will say just do whatever is fun to you, but I can't help but be a bit of a number cruncher
Anyway I just thought I'd pass that information along! If you (or anyone) figure out some definite formula, please pass it along!

-Meg