Is it possible without a simulator or remote opponent?
I explored this idea some time back when I was building up my collection and was trying out various mechs. I wanted a sand box to throw them in and see what they could do...
...so I came up with a very simple dice action system to try and create as much chaos on the map as I could.
Throw a lance I was playing against the dice mechanics.
I found that one hex map was the best size to play on as it kept the engagement close and the dice mechanics somewhat working together vs. a mech running off on its own.
For each mech weight class- light, medium, heavy and assault I used a 2D6 chart made up of movement and firing actions.
This was tailored for the weight class, which allowed them to act a bit in character- with 11 or 12 doing something completely odd- like a light mech charging and making a punch attack or if jump jets death from above.