I have a coffee maker that brews small pots. A few cups, mostly since my wife doesn't drink coffee in the mornings.
It has one of those filter baskets but, I started using the small filters since cleaning it out is a real PITA trying to get the grounds out of the built in basket/filter.
I'm thinking most of the larger brew stations with the paper filters would be as easy as anything else. It only takes a short time to set up a new brew and a few seconds to dump the old one in the trash.
The Keurig would however, allow your clients to brew one cup of their choosing when they wanted it. IMHO< that would be the best solution for the widest variety of tastes. One can have a dark roast, another decaf, and the next can have some sort of flavored concoction.