In Halo 4 i think you should be able to carry the two weapons, and have the option to use fists. Fist fighting in halo would make for awesome fights and machinimas. The option to fistfight would be even better of you had 1 on 1 fitfights or something.
I hope this is considered as an added feature of online play a well as custom games and campaign. i think it would be the best thing ever to be punching the life out of the covenant or other enemies in the game and finishing them off with a cinematic like move where you kick the enemy in the face or chest launching them back.