Shared parking - in and out of consortium

We are a consortium finding our heretofore-successful shared parking via ungrouped parking and dining seasons challenged by non-consortium-member organizations.  We are on RAMP.   Has anyone else solved this dilemma?  We are considering allocations to overcome the complications, and might consider a web cross-org solution if we could find a reliable and secure one.  I guess we might consider an integration like Arrive.  Would appreciate hearing from anyone who's dealt with this successfully.