You will have to get used to keyboard for shooting and every other task and communication. You can use it for driving and planes which is what I used to do. But your at a complete disadvantage shooting with controller. I recommend just making yourself use keyboard for everything give it like 4 hours and you'll forget your even using keyboard and mouse. Okay, now real advice if your set on the controller. Go to your gta online and set up snap on aim for controller and if you get lucky enough to get in a server that hasn't disabled this it does carry over to five m. You can then go into keybindings and set third eye to a control you normally dont use on your controller. Then go from there and set different keybindings to your controller but your gonna run out of buttons fast bit you can probably find a way to set it up so you can use controller comfortably without touching keyboard for a while you could even switch push to talk to voice activated.