After wrestling with membership categories and finding something that works we've settled on having to kinds of members--Residents and Roamers.
Basically Residents get to keep all their junk at their desk and get first pick of the conference room. Roamers get to bring in their laptops and find a free desk. The cost is figured on a 3:2 ratio. Whew, let's see if this works. It's more in line with other coworking spots, so it has promise.