Well, you know, NACRA products and their feasibility depends a bit on exchange rates. The topic is certainly interesting for those not living in the good ol' USA.

I definately think a 20 footer should be done within the scope of a formula class. That is the only way I think it could be done with success today.
I think the boat should be sloop rigged with spi and double trapeze. Width limited to max trailering width to make it easier on those not having mast up storage (requisite in the US and australian market I understand). I would want the boat suitable for both bouyo racing and distance racing with not too much sailarea so it could be sailed in strong wind areas as well.

With the F18 being as numerous as it is and lacking the versatility of the F16 (uni/two up) I think it will be a tough sell. There is probably quite a number of sailors who wants a 20 footer becouse $(insert reason here), but how to get them off the fence and how to bring new people to the boat.. Only hope I see is somebody doing a couple of boats and starting a true 20 foot formula class with homebuilds.