Possible drawbacks
- Maybe the interpaths are fragile/sharply delineated. For example, the path is a woven-string footpath that you must maintain contact with to stay on the path: running or even hopping is enough to leave the path, and a horse's hooves could break the string, destabilizing the path.
- On a less physical but similarly limiting weakness, the path could have a set limit to how much can be on it at one time. This limitation does not have to apply to weight: It could be heartbeats, or intelligence (too many mages try to travel the path at once, and the path starts dropping random smart folks out of it).
More suggestions welcome!