2 cents:
The ability to learn a new position should also be based on phenotype and other attributes. So, a 260# 1B -- let's call him... Prince-- would be somewhat odd looking chasing Texas leaguers in left. But, a 5'9 185# catcher who runs at 'b/b', may move sucessfully elsewhere.
LF is probably more valueable (and presumably more difficult to learn) than 1B: looking at UZR ratings, you see a greater spread --derivation from the norm of 0-- among LFers than 1B. The worst LFer (Ward) can be called Prince, Sr.