Can it run in a standard ratio screen then have artificially added black bars to simulate a different ratio
I think that is fine, as it makes running the game easier. As long a the effective screenspace for the game itself is a non-standard aspect ratio. If you can, try to avoid putting the UI in the 'black bars' to challenge yourself further.
that was the plan. I also wanted to have aspect ratio get worse as you play and this means I can alter it on the fly without causing graphical problem
That idea sounds kick-ass. Can't wait to see that in action.