I'm not totally sure if you are serious or not, but I'm willing to discuss this for a second. Why not? If Kennys Vargas has shown us anything, it's that if you are young, even if you have a larger build, you can probably still move pretty well. Sano is smaller than Vargas (not that I would play Vargas in LF). I promise you that if Sano played LF for the next 3 years, he wouldn't be any worse at it than Willingham has for the last 3. After that? Well, that's a while from now and a lot of things could change, but Mauer's contract will be up, so that opens up 1B/DH, and who knows, he might be half way decent at it.