What is necessary in a combat system?

[jok]

I would not want to use the system you are describing with a phone. I would like a full sized keyboard and mouse for all that input. Even with clever use of tracking state, auto-completion and combined commands to update the system that is a lot of inputs. I mean you could do it but it would probably require a level of master to use quickly. And even then I'm not sure it would go as fast as one (more in your head) done mostly in your head with similar mastery.

To Psikerlord: I forgot to say thanks for the link. Thanks, its an interesting idea, I'm already floating related ideas to see if any fit in my work.

I agree that a phone would probably be too small. Tablets or PC then. A decent WI-FI tablet for 100$ should do it.

The virtual tabletop Fantasygrounds has alot of automatization for D&D 5e already build in. A game from the ground up build with app support in mind would open up alot of possibilities.

One would have to be smart about the inputs and the UI and menus ofcause.