Then you just leave you self open to luck. You can't change your own weapons whilst also watching 3 different players loadouts and selecting a counter weapon in 5 seconds. The outcome of a lot of gun fights just comes down to pure luck if you picked a gun that counters your enemy rather than any thought into what you need to use. You need to be able to adjust on the fly to what you're playing against. If you do this in round you have the penalty of losing special ammo abd standing still in menu's for a bit. If you do it between rounds you have the penalty of not being able to change the whole suite of mods in time. It's a fair trade off. The only way locked loadouts work is if every gun in the game is perfectly balanced against each other. This is why competitive shooters have fixed loadouts. Destiny is not competitive or balanced so locking loadouts just guarantees 1 or more people will have a bad time.