I see where you are going and I like it in theory. In theory, I like it. Let me noodle it over. I am also thinking of splitting the difference and saying you get +3 to add to your out of Mech skills for that 1 XP. You could take 3 skills at +1 or 1 skill at +2 and another skill at +1. Then I would set limits on what your maximum bonuses could be, for example:
1 skill at +3
4 skills at +2
2 skills at +1
That way no one player could be master of everything and create some diversity amongst the unit.
Of course that starts to get complicated.
Also notice that I have added another skill (Perception). If anyone would like to drop one of their pre-selected skills in favor of Perception, you can do it now, and only now.
In addition I have added a new Advantage (Lostech Mech) that allows a player to start with a Star League Era mech at character creation.