I'd like to clarify that this isn't anything as simple as pairing up lab partners at random or something.

Due to the importance of compatibility, after graduating together, a Tuner-Receiver pair is intended to be permanent. They're intended to work together from then on. Since, well, they're compatible. It's hard enough building that kind of relationship the first time.

This is part of why I'm not really certain on RNG, and if I did do it it'd be a much more limited version of it.

That and some people might have a specific type of character they'd like to be paired with or something like that. I do with Rika, for example.