I didn't expand the character RAM actually, instead I saved them in the area where B/W/L numbers are stored. I left the actual BWL numbers alone, and replaced the hidden "favouritism" stat which tracks how many times you've viewed/selected a unit.
Because only characters up to 0x46 can have BWL data, characters above that do not have room to save their skills. Instead, they look up the skill list to see what skills they should know at their current level. Since these units are mostly generics or at least enemies they don't need to account for branching promos or using items or anything like that.