Question: In trying to set reasonable limits on a PC's usage of the polymorph chain of spells. Is it plausible to require that the PC have some form of interaction with the target creature? Or can a PC polymorph into a creature that the PC has only heard about? Or read about in a book? Or seen just a painting of? From a solid role-playing standpoint, it seems reasonable to require that a) the creature exists in the multi-verse that the DM is running, and B) the PC has some knowledge of the creature. What is the minimum "knowledge" that the PC must have in order to polymorph into such creature?

Answer: 
I've taken to a risk v reward method for Polymorph. I make only one simple alteration. If you nat-1 on a Polymorph, you accidentally summon whatever you were trying to alter yourself or others into.

Nice and tidy, it deters anyone from doing anything too terrible or dangerous and is rare enough that occasional massive risk can result in great fortune. It retains the power of the spell, while preventing it from being abused.

A potential addition that I considered but didn't include was increasing the failure rate for monsters that the player hasn't encountered before or hasn't passed a knowledge test to know about. That could work, but the risk of accidentally making the battle unwinnable seems to be enough for my players.
I recommend handling polymorph spells the following way: The player casts polymorph, wildshape, etc and tells the table what he's turning into. If anyone at the table then exclaims any of the following phrases: 'What?!', 'The hell book is that from?', '', 'That's (ridiculous/stupid/a travesty)', 'Quit being a douche', or 'Nuh-uh', then the casting fails and he gets to try again next round.

The best solution for all player problems isn't codifying a rule base to eliminate abuse, it's making it immediately clear that Player X's shenanigans are making the other people at the table have less fun.