Took a look at an old turbo [off a tractor] in the garage, and your idea should work for mdf and such, lighter cuts on relatively soft material...If you lop off the exhaust side and make some kind of a spacer to get two bearings a little further apart it will help accuracy..
the screen in the inlet side is definitely a good idea...
It's not going to be really tight and accurate, but then the cost reflects that as well...
Do you have any idea of how you are going to adapt a collet on the end??
enjoy..