I have high insteps. What works for me (well, at least for one of my feet) is Salomon Synapse Wide boots. Salomon makes two models in wide sizes -- the Synapse is the stiffer model and the other is has a softer flex. (I think it's the Dialogue, but don't hold me to that.)
Also, I have Flow bindings and like them a lot. It can take a bit of work tweaking the Flow bindings to get them just right, but once you've got it, you're done. And it'd not like straps where you might get it just right on one run, then have pain the next time. I know exactly what you're saying about tightening traditional strap bindings enough for control leading to agony (and not tightening them enough leads to lack of control, at least for me).
I mention "at least for one of my feet" because I have still have a problem with one foot (my lead foot). I've finally come to the conclusion that I need different size boots for each foot (I'll still go with the Synapse Wides). So next year I'll be the guy on the hill rocking two different boots.