If by not much larger you mean both the inside half and outside half combined on top of a lens mount, then sure.
But this topic is about the X200, and personally i'm hoping for the same lens, but with close range correction, a.k.a. a floating element. To keep its character, but maintain performance across the whole focusing range.
I don't mind adding a few millimeters if that means they can add a proper manual focus mechanism, or possibly a standard filter-thread.
I don't think it would be good to go 28mm equiv, you'd need to get very close to get right in the moment (something that i think the X100 is meant to do), or shoot only wide angles, which is not often ideal. Of course sometimes it is, but not as the only option. While the WCL is a greatly underrated addition that offers that already. It works perfectly with almost no quality degradation. Looking at the optical construction with the WCL attached you can see why, it looks almost like it was designed like that. The TCL on the other hand, not so much. A very unnatural looking lens projection, not bad in performance per se, but not very attractive, and way darker than it could be.
The best thing i think would be a second body option, with a 35mm F1.7 (50mm equiv) or similar, much like the classic Yashica Electro 35. And a larger magnification OVF to match. I think that would be a huge success. Possibly as much of a game-changer as the original X100 was. With the Ricoh GR, Nikon A, Leica Q, and now X70 all going wide. Let us hope Fuji has seen the light, and use it to fill that huge void in the market that is a 50mm equiv fixed lens camera.