Some melee combos require the Aim/RMB to be pressed, usually this is held down (atleast by me) this results in if you pause attacking you will aim your weapon, and if you have the melee attack on LMB toggled on, can be awkward having to press your melee key to go back.
So my suggestion is to have another toggle that disables the weapon aim functionality while using a melee weapon, and maybe make swapping to guns with the manual key faster if you still want the fast paced swapping. But even as is i would take slow swapping for this addition! The other option would be to have a "legacy" toggle where it would go back to how it was. (but with quick melee performing the weapon combos rather than the limited quick attacks of the past) Also its impossible to aim glide with the weapon in hand currently (meaning cant aim glide then smash attack with the LMB)
I think the best option would be have it is now, But also allow Hard swapping to melee (like previously) that would disable LMB/RMB swapping to the gun, essentially allowing the best of both worlds, have the quick flow when i want, and have the Pure melee when i want.