IMO making it a control key is a better choice (I tried both at some point) because chording with awkward keys is worse than just pressing them, and the control keys are placed awkwardly on most keyboards. Since you can end insertion mode with ^[ you then have a pretty comfortable chord that doesn't stray far from the home row to replace the escape key.

I had a tool on a mac that would make caps lock equivalent to escape if it was pressed and released alone, and control if it was chorded. Sounded great on paper but I underestimated how often i press control before realizing I don't want to perform a chord.