Caravans do this already -- they give XP to the companion running the caravan, not to the player who owns the caravan. Pretty sure this is working as intended.
...wait, really? That's terrible. So even if you have a learning rate of 0 in a skill, you still gain character XP for using it?
It's not about being weak or strong. It's about clear oversights. The Aserai Footman was clearly designed (looking at its equipment and skills) to be a T2 unit, but it's T3 by mistake. The Aserai Tribesman (T2) isn't even an upgrade over the Aserai Recruit (T1). Their stats are identical. It gets literally nothing but a better helmet. The Recruit is a new unit that was hastily added to the game when it was clear that mamelukes weren't available at all, but the ad-hoc "fix" to the unit tree left big problems and it needs another look.