What do you mean by supportable? I was happily using mono for a number of custom servers in a similar way a couple of years ago. You don't need any huge frameworks to make mono really useful.
Writing web apps may seem like the only thing people do lately, but it's not. Given a choice of a number of languages and runtimes available 5 years ago for example, .net/mono was a perfect choice for a daemon dispatching jobs to a number of usb dongles where having a good ffi (p/invoke), nice io abstraction, async actions and database interface was important.
This is something you write from scratch. No big frameworks are involved. If I ever find I need MVC.net, I'll probably go with a completely different language.