better challenge system

i want to see a better challenge system in Halo:CEA and Halo:4. i want something more set up like call of duty. yea i know halo is not call of duty, and i dont want it to be. i just like the challenge system they have.i would like to be rewarded for getting kills with different types of weapons, or using different types of equipment, or doing something like sticking a flying enemy with a plasma grenade.
i know that u do get rewarded for getting kills while flying, etc. but i think the challenge system could be better. it would also make players step away from there comfort zone and not use the exact same load out every time. they would have to experiment more with different weapons and different tactics. just a thought