Too late now, but they had a fairly easy way to do this.
They should've just added the class gadget, a class perk tied to gadgets, and a weapon proficiency for the class. So you could still play the same way you did before the patch if you wanted to, but, if you were "out" of class, you would not get any of the benefits of being "in" class.
Examples:
Support class gets defib + ammo and med packs on a cooldown, but any other class that uses them would only get one (and would need to respawn or use an Angel's crate to reload them).
Engineer class gets repair gun + be equipped with extra M5 and/or FXAA storage and could hold 3 at a time, but any other class would only get one.
Class gadgets work better in class (faster/shorter cooldown) than gadgets used out of class.
So Sundance could still use M5, but would only get one. Mackay could use an ammo pack, but would only get one.
My thing is they only went halfway into classes anyway, so if they were going to just do that, then they could've done what I described above.
Tradeoff from previous titles = (+all weapons accessible + Specialist Gadget + Specialist Trait) = +3
Tradeoff from launch of BF2042 = (+Class gadget + Weapon Proficiency - access to specific gadgets) = +1