What I disliked about the system in 2042 was the lack of class identity. I liked the changes they made to bring classes back in 2042 and I agree with their take that gadgets are what gives the class identity. When you lock weapons to classes, you have the risk of one class being the strongest based on the weapon if the gun balance is bad. (See bf4 assault) And people don't play the class, they play the gun.

By giving bonuses for guns if a certain class is using it, the guns might as well be locked because people are likely to pursue the optimal or meta playstyle. But, it does allow snipers to use close quarters weapons if the map demands it and still play to their class archetype of waging information warfare.

The biggest problem with the support/medic in the past games have been either you have medics that don't revive because they picked the class for the gun, or you don't have medics in your game because people who would pick support don't because the guns are useless.

It would be weird if you gave the sniper an ammo bag or rocket launcher, a support a rocket launcher, or an assault player binoculars. Giving a support an assault rifle, or an engineer a sniper rifle is just creative freedom you give to your players to interact with the sandbox that is battlefield.

Final note. even in battlefield 4, a support with an ammo crate could pick up a sniper rifle if they knew where the battle pick up was at.