The free squad slots that I mentioned should be permanent that would be useful later on as he unlocks more squads.
Regarding the OP idea, I do think XP boosts for low level players with a special value depending on how many high level players on the enemy team with more high level players, the higher the boost for low level players. There are cases that only 1 guy full of high level weapons and squads can influence the whole match like in Normandy with full MP43, FG42 and MG42 squads can carry the entire team even when the rest of the team are armed with just bolt actions.