It's apparently a server-side option. Hoping to see most servers allow all weapons, without the unlock system. I don't really see what's so great about them. They're like the system in which you get dog tags for knifing - they encourage individualism and rivalry and hurt teamwork.
Secondly, when you're on a team, your experience alone gives you an edge over the enemy. Pit a team of people who've played for 1-5 weeks against a team of people who've played for only a few days and barely gotten into the game and you'll see what I mean.
Thirdly, it's confusing and hinders coordination. If half a team's troopers don't have homing beacons, flechette launchers, or deployable deflector shields in a vehicle-rich map, suddenly their tactics can change pretty drastically. This makes it harder to coordinate a team, and to keep an overview of who has what.
Finally, FS kits don't have a 'good' gun, a 'better' gun, and a 'greatest' gun. The Trooper class, for example, has a weapon for long, short, and medium range. These are equally good, they just have different uses - as the devs have stated, they make up 'sub-classes' within each class. Pick the E-11 and you're assault. Pick the long-range rifle and you're a sniper. So to make some of these weapons unlocks makes as little sense as making individual classes unlocks.
Getting more stuff as you play is great for RPGs, bit less so for a free-for-all FPS, and not good at all in a teamwork-oriented FPS.
"One of the bitches actually gave birth while she was attacking, and her puppies joined in on the carnage."
--the awesomeness that is Boatmurdered.