You make the claim that "80% of our balance issues could be solved by a closed weapon system," but I'm not sure I see how that would address most of the game's balance concerns. Could you elaborate on what specific issues you think it would solve?
A closed weapon system reduces player choice by tying weapon selection to class selection. Personally, I see class identity as something that should come primarily from gadgets, abilities, and battlefield roles rather than weapon restrictions.
In previous Battlefield titles, there were situations where I wanted to switch to a class that would better support my team, but I hesitated because I didn't enjoy the weapons associated with that class. In other cases, I would switch and immediately find myself at a disadvantage because I was forced to use weapons I was less comfortable with.
Allowing players to use their preferred weapons while choosing the class that best fits the team's needs can encourage more role flexibility and team-oriented play without eliminating class identity.