The idea would be pretty simple.
Coffee call could be 10 mins and allow 3 people in a call
Espresso Call could be 5 - 7 mins but only be 1 to 1 call
The incoming call would clearly identify the type of call(CoffeeCall | EspressoCall) allowing you to decide if you wish to take the call.
Problem is see might be with notifications you might miss espresso call simply because you don't alway have your phone in your view.
I like the idea, because many coffeemachines also have these two buttons, a small cup and a bigger cup. I would maybe call it espresso (small cup, 5 mins) or cappuccino (bigger cup, 10 mins) then?
On the other side it would also make the app more complex to use, because you need to decide on the spot whether 5 mins or 10 mins would fit. That's another thought process where I'm not sure if we would like to stimulate that. Rather find something in the middle then maybe? Or give opportunity to extend the call during the call?