I would guess this would be a large undertaking but it would be VERY nice to add the ability to swap out the output browser to a different browser. With new IE exploits coming out every other day, and the fact we use firefox 95% across the enterprise, it would be nice to preview in that browser instead.

I know about those security issues caused by IE. Actually you're safe while you're working with your own site (until you're the developer of such exploits...)