Besides the obvious "Allow Trusts to be used in the party (without the benefits you mentioned) when you're unable to fill the slots with other players", really the only thing I can think of is to have a way to quickly get the group to where you're going so you can get started faster.

Obviously Home Point warping is already a thing, but maybe have a way to let players teleport (within reason) to their party when they're on the same map or region as them, or something similar. Partying should be fun, shouldn't require alot of start up and maintenance, and if someone has to drop, getting a replacement shouldn't be an ordeal.