Well, right now Cruzbikes are
Well, right now Cruzbikes are fun and pretty easy to ride although some have struggled with them. Their market is growing and more and more people are attracted to the format.
All of the videos I've seen of rear wheel steered bicycles suggests a rear steered Cruzbike would be very hard to ride with only a few mastering it (if any) - not a good formula for success unless you are targeting miniscule sales and the ultimate demise of your company.
The only truly mass market appeal for a rear wheel steerer that I've found is the
Velayo Velomobile. However, the creator is currently on some sort of hiatus and has explicitly expressed no interest in exporting outside the EU.
The next most viable would be
Robert Horn's S'trike, a tilt steer FWD delta trike. Not technically a rear steer although some consider it to be so. This one looks like fun, but it isn't a Cruzbike MBB, FWD...
-Eric