I'm not sure I can see them putting out a module for more than £50-60.
I think the piecemeal model suggested above, similar to Rise of Flight's field mods would put me off. What's the point in paying for half an aircraft in effect? Rise of Flight's structure was different, because these planes were frequently modified in such ways.
For that reason, I think that structure would work better in the Shark, as there seem to be as many variants as there were models made. However, would the fragmented user-base and split development priorities be a good thing overall?
Edit: please note, I really don't know what I'm talking about. I know nothing about how to price things or how to run a business.