In the "how bad can it get" category, in the No Whining Progressive we had an owner play 1984 Andy Thornton at catcher for 162 games.
Thornton is primarily a DH, but did play a little 1B in 1984 and so has a D/D- rating there.
In 162 games as a catcher, he posted these stats:
.965 Fielding Percentage (this was actually much better than I expected)
374 passed balls (2.31 per game)
11 CS in 202 SB attempts (5.4% CS)
Basically, a complete disaster. Thornton hit pretty well (.317/.401/.478) but in my estimation his defensive performance more than completely erased everything he did on offense. On net, he was the worst player in the league, way way way below replacement level.
In case anyone is interested, the NWP does not reward tanking in any way - our draft order is determined completely randomly and there is no advantage to having a bad record - so this was just a case of an owner who did not have a regular catcher, and opted to use his best remaining hitter as his catcher.
My conclusion - there is no player in all of WIS, not even 1920-21 Babe Ruth, who hits well enough to justify playing him out of position at catcher. Unless you are playing in a theme that requires it, it's a disastrous strategy.