No reason it could not be done, there have been several all-metal RC kits offered over the years, Jerry Nelson (of Nelson R/C Specialties) is working on a couple designs he plans to offer at some point (metal framework but fabric covered). I remember seeing pictures of an all-metal Bulldog (British built single engine) many years ago in RCM and an all-metal P-51 model here in the States.

However, in most cases a fully metal skinned model they would be heavy for the size, very hard to build (skill wise), relatively fragile, and very hard to repair. And they would be aluminum, not titanium (Besides high cost, it is notoriously hard to machine, cut and drill - try working with some Ti sometime, you'll see. ).

I have built 2 full scale homebuilts, one all composite (Vari-EZ) and the other (HP-18) had a composite forward fuse and metal tailboom and flying surfaces. I would MUCH rather deal with wood or composites....far more forgiving. But that's just my opinion, YMMV.

Barry