Repurposing 2010 21.5" iMac as a second monitor

So right off the bat, I know this can’t be done in target display mode, I bought the cables, tried, cried, did some reading, cried some more.

I’m pretty comfortable with opening it up, I always fix my own stuff, so I was wondering if there are any hardware mods I can buy that will allow me to turn it into a second monitor.

I would like to keep it within it’s iMac shell if possible, and it does have the mini DVI output port, I was after something that might be able to allow this port to become an input as well as an output.

Anyone have any experience doing anything like this?