...the bitchy manager was like "NO way. I don't want you starting this stuff here because then everyone is going to start doing it. I don't want to start something like this." 
Yeah, and that might attract more interest & business.

I’ve trained at two different gyms in which members were allowed to (and did) use chains, etc.
They did their thing, didn’t bother anyone, nobody bothered them, and there was no mass epidemic of other members bringing and setting up chains on every bench (how many trainers are serious enough to do that, anyway).
A few people watched and asked questions. The PL’ers were very cool about it.
Sounds like you have the right type of personality, and you obviously took the right approach with the new place.
You may even end up doing what I did and become friends w/ the owners…if you want.
Some people prefer to avoid that inner-circle, but I
am extended certain courtesies that are not offered to everyone. Just don’t abuse the privilege, and make sure to reciprocate and throw some kind acts their way.
Best of luck, and keep us posted.