Not enough time at beginning of matches to change loadout
Especially for modes like Rush or Breakthrough where every second counts to get to the objective first, the absence of a timer before the beginning of a round leads to complete chaos.
Often times you get 3 seconds to just barely even select your class, before you even thought about loadouts and gadgets.
As a simple example, as an attacker, of course I want to take smoke grenades to make the path to the objective easier, or take a vehicle protection perk instead of anti armor because I want to keep my tanks alive, while the enemy has no to destroy. If I want to change my loadout, I miss being at the objective and that is a significant disadvantage especially in Rush. As a defender, I often cannot deselect smokes because I need to hurry to stop attackers from charging.
This results in a constant flow of random chaos and the squad perks and gadgets you created get barely used. A simple 30 second timer after the game found all players to participate would solve this.