You can refill ammo, hp, and blocks there, essentially it is like respawning but without the wait time. So why not do it with weapons too?
If you are standing on the tent and you press . then it instantly changes your gun. (If anyone is wondering, it is possible to change weapons on the fly, so don't worry about the technical aspect!)
Since people are pushing for an option for the grenade spot (health packs, ammo bags, alternate/extra blocks/ etc) that should also be changeable by clicking . (or perhaps /), and of course if you are standing on the tent then it instantly changes without killing you!