To answer the OP.
From my experience, it wouldn't fly. I never charged for table space in my store and I've heard too many stories from customers and former FLGS owners that it doesn't work.
The flow of events from these anecdotal sources is:
1. The freeloaders stop coming to the store.
2. Regular customers (those that buy stuff and play in the store) may pay initially, but then they stop coming to the store.
Net result is you have less people playing games in the store and less sales. People playing in the store, whether they bought the stuff from you or not, is most always a good thing. Folks will watch the game being played and may then buy a copy from the store or ask for a special order if you don't carry it.
From personal experience some freeloaders can be annoying bunch. They get warm in the winter courtesy of me paying the gas bill and cool in the summer courtesy of me paying electric bill. That said, if they are part of a local gaming group that plays at your store, you just put up with it. You can't afford to piss off the gamers who do play at the store and do buy stuff from you.
All that said, I did occasionally turn off the heat on a given freezing night when there were no paying customers in sight and all I had were freeloaders in the store. "Hey Rich, it's cold in here."
"Yes, that's why I'm wearing my coat."
Thanks,
Rich