CQC-Control-Scheme:
Preface: I will refer to no ADS, no point fire as neutral stance.
L2 (toggle): point fire
L2 (hold): full ADS
Make it that when you are in point-fire mode and then hold L2 to go into full ADS and then let go of L2, it returns to point-fire mode. When you go full ADS by holding L2 from neutral stance and then let go of L2, have it return to neutral stance.
L3, R3 (toggle): lean left and right
L1 (toggle): hold breaths whilst in ADS
This would still be a bit awkward but you would mainly use this for sniper shots from a strong position. So here having to use middle finger to hold L2 and press L1 to toggle hold breath would be ok.
Love your game, hope for many years to come!