One for the combat rules committee: consider the use of fractional BAB for class advancement.
Currently, character classes advance BAB as defined on a chart. Those chart values are based on rates: poor (50%*level, e.g., wizards), average (75%*level, e.g., clerics), good (100%*level, e.g., fighters). Chart values are rounded down.
When multi classing, it is possible for a character with 2 “average†BAB classes to have a lower BAB than a “poor†class at the same level. For instance, a cleric 1/monk 1 has a BAB=0, while a wizard 2 has a BAB=1.
Fractional BAB would advance BAB using the rate defined above when adding classes, so wizard 1 has a BAB of 0.5. Still rounded down when used in game. This has the effect of slightly bumping up characters that multi class or take prestige classes that do not have full BAB. So a cleric 1/monk 1 would have a BAB of 1.5 = 1.
Haas had a span where his BAB did not increase for 3 levels because he went cleric-monk-prestige class, all of which had average BAB but because of rounding in the table there was no noticeable change in use. Fractional BAB would have given him a +2.25 BAB adjustment instead of 0.