Looking at this from a field owner's point of view;
If a field isn't very busy, then it's not cost effective to have staff at the field in the hopes that enough players for a game will show up. Chances are they are barely making money on the days they are open, so paying staff on days where no game ends up taking place, will lose any that they make on the "good" days.
We ran for quite a while when we first started and only opened on days when we had enough deposits. It allowed us to be "profitable" and we built our business from there. I think it was 7 or 8 years before we committed to being open every Saturday and Sunday. Both our competitors have been open for more than 20 years and still haven't committed to regular hours.
One person handling cash...good idea. I wish we cold implement such a system. Employees steal. Not all, but enough to have it hurt. Do some research and you might be surprised to see how many people are willing to steal from their employers and how many will look the other way when others are doing it. I've had employees who were personal friends steal from me. It sucks and it happens, so if the owner wants to be the only one handling cash, I don't blame them.
If a field is not very busy, getting a group of renters coming to play is great. Having a few gear owners "drop-in" and shoot them up, may hurt the field more than it helps.
Maybe suggest that the field open one or two specific days per month (i.e. 2nd and 4th Sunday of the month) for gear owner drop-ins. Then start spreading the word among the local gear owners and see if you can get enough players together to make it worthwhile for the field to be open. Once these things catch on, sometimes they take off and get a momentum of their own.
Running a field that is not well attended is difficult and hard to keep afloat. It's difficult to balance convenience for the customer with keeping costs in check.