Replace the current Basic-to-Expert skill system with a skill tree. Each role is given affinities for skills in this tree, which represent how easy it is to for them to enhance that skill. The baseline value for an affinity is 100. The lower an affinity number, the better it is for that role, because enhancing a skill costs (some base cost * affinity / 100) skill points. Skill points are awarded on each level up.

The end result is a system without arbitrary skill caps, where anyone can theoretically become expert in whatever they want, but if it’s something they’re unsuited for they’ll have rendered themselves unable to become skilled in much else.