I'll have to agree with carrellh; the UCDs are a bit too fragile for a trainer... IF the student will be on the sticks for landing. If you're talking a buddy box set-up and just allowing the student to fly the model for familiarization, with the master radio/instructor handling things close to the ground, then yes; your reasoning is sound.

Same thoughts on these as a second airplane. If the pilot is past the landing prang stage, then by all means... the UCDs are very tame on low rates.

But they will take practically NO abuse. I realize anyone can have a bad landing. The results of that are why I hold the opinion I do. The UCDs are built very lightly.

That said... no doubt someone will chime in here and write that they have pounded their's in with no damage after doing an inverted double jump-back waterfall, etc.... Perhaps. But I do a bit of teaching at our field, and a UCD of any size would not even make my list for rookie pilots.

YMMV...