How about the idea of creating a new company with synthzone members as some of the main contributors of the features ? Who knows we might just create a very profitable company, or at least a decently profitable company.

How hard would it be to come up with a prototype ?

Maybe start with the keybed of a popular synth/arranger. How about start with the keybed of the Yamaha DGX 500 ? and then we can modify the rest to suit 90% of the synthzone members.