That's an interesting question!
I am sure there are those who have fitted a catch can to their MGF, but I bet that has been done in the context of more extensive engine modifications and individual throttle bodies.
The purpose of a catch can is not really for performance benefit as far as I can see, but rather to keep the inlet system clean. On any standard internal combustion engine, the crank case needs venting - and if you vent the crank case, oil vapour will be released to the environment. Old car engines do rather reek of oil (all part of the charm!) but this is not acceptable for modern environmental standards. Since oil burns, manufacturers therefore vent the crank fumes into the inlet system. On the Rover K-series, there's a pipe into the plenum and also to the throttle body. Once ported into the inlet intake, the oil fumes are then drawn into the combustion chambers and burnt.
On a standard road engine, there is no need to consider a catch can. Or at least not on a Rover K-series. It runs cleanly, and oil/soot deposition on the inlet valves simply isn't much of a problem. I suspect this is because the port injection of fuel keeps the inlet tract nice and clean. Direct cylinder injection however may be a different kettle of fish!
On cars with throttle bodies, one needs to consider how to handle these crank case fumes as you have discarded the existing throttle body and plenum. Not sure how this is done on the VHPD derivatives (as found on the MGF Cup cars, but also on Elise and Caterham 7), but on aftermarket solutions, something like this:
Here, one of the vent ports has been blocked, and I think the other either runs to the intake plenum or to a catch can (that can't be seen).
In summary then: yes, it can be done and no, not much benefit unless it is a part of (or mandated by) much wider engine modifications.
