Re: How does anything stay locked?
 

Yes. Although, the more mana and other power an IQ 18 wizard has access to, the less I'm liable to expect him to want to do routine bank vault safety duty.

Though one mitigating strategy, is to make sure there are always at least two gates to a otherwise-inaccessible treasure vault, and NEVER use the last gate unless you're in a position to create a replacement. (Because you might crit fail and use all your mana trying to stabilize the gate... meaning no second chance unless you had 100 ST available.)

If you have a backup gate, then you don't have to have the gate wizard present for every crossing. You just need him to make you a new gate to replace when one goes down.

Of course, it becomes a problem if circumstances ever develop that there is no gate wizard available, and you really need to access the vault...

Re: How does anything stay locked?
 

I.e. that's the case for ensuring that each gate has at least one side at a gate station that has a dozen wizards on duty.

Re: How does anything stay locked?
 

A separate Transport Guild shouldn't need to worry about popularity because of its massive revenues (like Dune's Guild).

It would maintain a lock on the Gate and Control Gate spells through threats, and assassination, and divination.

Re: How does anything stay locked?
 

Gate stations should have maintenance gates connecting to at least a few service hubs. When a gate starts to flicker, automatic systems alert a service crew. Redundant gates allow service to continue while a crew is on its way. They would use a Gate to get there, so that involves a risk of Gate failure of course.

In a dire emergency where a Gate station becomes completely cut off, the Guild would call in a special agent with knowledge of their Gate stations, Long Distance Teleport, Gate, and Control Gate, carrying power stones and several limited wishes.

These agents would be formidable but probably also make good hostages. Someone could probably lure one by destroying all the Gates at a station...

Re: How does anything stay locked?
 

The two spells backing every gate station are Create Gate and Ward.

Anybody with hostile intent who steps into your gate network faces a dozen alerted wizards and the muggle guards. And there is no saving throw against this alarm.

For a minimal defensive setup see Hexagram #4, page 32. Your orcs of ill intent step into a room that has 15 pacifists, 3 of whom are wizards plus a dozen unarmed heroes who lack weapon talents. The hardest part is finding the addresses to send letters to the families of these dearly departed orcs.