It can be difficult to map an fps with so many keybinds to a controller, but it's not impossible. Some compromises may need to be made.
Leaning was a big part of Rainbow Six Siege. To make up for the insufficient amount of buttons on the controller, leaning was only made possible while aiming down the sight. (The leaning action replaced the sprint/melee actions while aiming down the sight, using the thumbsticks). It looks like autolean may be our only option, given that there's a hold breath mechanic that will need to be bound to one of the thumbsticks. Gamers don't like new/strange controls.
I checked the amount of buttons for binds, and it looks like all we have for the special actions are the d-pad, L2 and R2.
Left on the d-pad may need to be used for a weapon wheel, similar to the likes of GTA V and Turok Rage Wars.
A quick tap of that button could be used to quickly swap between your primary and secondary.
Up could be used for laser/flashlight, down could be used for gasmask/nightvision,and right could be used for rate of fire and fireteam support menu.
That just leaves us now with L2 and R2.
L2 will have to be used for the teamchat radio button with the automatic mic defaulting to local chat.
All that's left is R2 and the menu button (left side of touch pad on ps4).
The menu button will be used for changing classes.
R2, being our last available button, can be used for the voice wheel, so you can call out enemies.
A stripped down version could do, with only options for "enemy spotted","I need a ride","I'm going to objective",etc.
Maybe use of the PS4 gyroscopes to assist in aiming could be implemented. (Splatoon uses gyroscopes in addition to the thumbsticks, from what I've heard)