K.

I've been suggesting this for ages. It would be a great mechanic.

(Grafted from my dead thread and resurrected here) On the flipside to fostering personal loadouts, it could open up some really robust customization for user-created gametypes in competitive multiplayer. Now, I know Bungie has said you'll be able to take all your gear from co-op into competitive, and their focus in Destiny seems to be less about e-sports than with previous titles, but they're known for having pretty deep custom game options in multiplayer. And being able to specify from and tweak a huge arsenal of weaponry is just crying out for attention from the hyper competitive FPS community, which favors same weapon/gear starts off of spawn or at least finely tuned and balanced loadouts. If you're only in the game for the competitive scene, you'd still have whatever banquet Bungie lays out for the entirety of their audience, which I'm sure will be worthwhile and fun. But if you wanted to get really in-depth with gametype analyisis, design and balance, you could try to amass an arsenal, take them apart and try different combinations of parts, building a whole catalog of different guns with different bloom, bullet magnetism, recoil, weapon damage, rate of fire, optimal engagement range (red reticule range if we're talking Halo mechanics), a whole host of options. This could launch a whole niche of the Destiny ecosystem that runs through activities to collect weapons for parts, that does their own weapon tuning for testing competitive gametypes. If they discovered something that really took off, it could be incorporated as something anyone has the option of playing in some public competitive arena setting rather than just private custom matches. Granted, you could still reroll for loot to get the weapons to test out default loadouts with but it would take much longer to find just the right weapon, and you just wouldn't have as many options to mess with or be able to really look under the hood to see why some weapons have certain attributes.

Don't forget more recent arcade-y games like Loadout! Probably not something so over-the-top, but there you go, every part has its own effect (but you don't cannibalize so much as build your gun from scratch).