Actually, I think that is the perfect solution. Feats are now meant to customize your classes.
Rogue A is a dagger user. He's happy with the light blades and and the x-bows he as learned to use in the city streaks. He spends his feats and abilities improving his stealthiness and the like.
Rogue B does not like being limited to daggers and light blades. He's a street thug, and thus has learned to use a slightly wider range of melee weapondry. He spends takes strength-based combat powers and spends his feats on expanding his roguish weapon abilities (and now light maces can be used for any of his abilities as well). We don't know the mechanical difference between a light blade and a light mace...it could very well be large enough to require the restriction.
Rogue C is an elf, good a sniping with a bow (multi-class ranger). He spends some training (i.e., a feat) to use his archery skills in conjunction with his natural bow abilities and his ranger levels. Again a bow might be significantly better than a x-bow in 4e, hence the need for a rogue to take a feat to use his rogue-powers with them.
Rogue A, more stealth. Rogue B can use maces with his rogue powers. Rogue C can use bows with his rogue powers. That is exactly what feats are meant to do in my opinion: customize your character beyond the ability choices. I hope they do supply a couple feats to let rogues use their abilities with other weapons.