Naturally, this limits a lot of character options.
Conclusion: Start each character on equal ground. Everyone chooses 2 ability scores; these are guaranteed a +5 to-hit, minimum, plus whatever weapon bonuses there are. Weapon Expertise is now banned.
This puts everyone on the level of an 18 stat plus WE, which means you can actually explore some of the more interesting options in character builds (battleragor vigor from the Martial Power book, for instance) without sacrificing full optimization.