Teeeeeeechnically you could do it the PVP way, but you'd have to macro in unused hotbars and use multiple macros and such and it's a pain. It's also super inefficient in the end, as mentioned, because macros don't queue up like normal abilities meaning you might have to mash the same one a few times to go off. But it is doable, just a lot of setup and taking up like 3 or more macro slots for one 1-2-3 combo. I mostly only use it for BLU to reset my hotbars to include the macro commands I use, since I have to change my whole loadout sometime.

As stated above, I don't recommend you macroing it as opposed to just the standard 1-2-3; it's more effective to have control over your GCD actions to weave between them better.