A basic quick render would be a nice feature for a later date; however, you may want to take a page from another "modeling-only" program. Since most, if not all, rendering packages on the market support a command line interface, why not offer the ability to the send the scene directly to a 3rd party renderer via command line? That way, it circumvents not being able to render an image without either closing MoI and Opening the scene in another package, or running both packages simultaneously.

Just my two cents.