We ran smack dab into this problem in the campaign we just started, with a bladebound magus who was somewhat less than thrilled when he realized that the weapon enchantment from ABP wouldn't interact well with his black blade.
We solved it by giving the magus a gold reward equal to the bonus he would normally grant to his sword. Whenever the other party members increase the bonus of their weapon, he receives an unexpected inheritance, wins the local lottery or otherwise come into some extra cash. It's a little forced, but it solves the problem fairly well.
Yeah, one of the PCs in my game is a bladebound magus, and I was thinking of ways to compensate him. The blackblade still gets its enhancement progression faster than ABP at lower levels, so there's that.
At first I thought I'd let him add his weapon ABP to his arcane pool enhancement, but then I realized he'd be able to give his character a vorpal weapon at level 9 - the PC's current level - and I'm not entirely comfortable with that.
I'm mulling just adding the ABP weapon bonus as extra points to his character's arcane pool.