This is already possible, just not directly via the client. If you do it via the client you always end up in a multiplayer lobby. You'll have to start the game directly. You can (usually) find it here: C:\ProgramData\FAForever\bin And then just start the executable. You can start a skirmish from there.

You might find adjusting the game speed to +1 or +2 to be helpful. It's still very manageable to play at these rates and they'll cut down game time.

Left or right-click on the text Choose AI for autofilling This will open a dropdown menu to select an AI (also active AI mods)

When you setup the game make the speed adjustable and then increase it a bit in game, +1 or +2 is barely noticeable in terms of getting things done but will conclude the game signifigantly quicker.