I really don't see how stack size is any indication of skill. For one thing on some sites you can buy in for 200bbs or more depending on the table. Even disregarding that, all it takes is a couple suckouts and a terrible player has a 300bb stack. If you just sit down at a table and place a "skill level" based on stack size, use that as a read and play a certain way against them, I highly doubt it's +EV.