Giovanni, that's the first time I heard of anyone turning a keyboard into a module! It's very ingenious!
If Yamaha told you they're not going to make a Tyros module, they probably won't, so we can stop wondering about that. However, they also told you, "we make keyboards", and everyone knows they did make modules like the Motif Rack and some previous ones. So maybe, the guy you spoke to has no idea. Interesting.