I am currently in a similar situation. I found a school with open time slots, and rented specific blocks of time that i could train my own students, in whatever way that i want, and we had a lease drawn up. So my students who i trained from the beginning are mine and mine only, and if i leave, they go with me, and all im really leasing is the four walls.
If your wife is worried about her students being stolen, i would recommend she take her students to the local ymca and rec center to get her teachers hands out of the pie. And there is not now nor has there ever been any type of regulation that says she has to train with just one person. She is free to find a teacher who is much more suitable to her likings at any time.
Remember, a piece of paper that says "can only train someone to second degree" has no bearing whatsoever to anyone except the guy that signed it. if i tell my students they are all 87th degree black belts then thats what they are. because i as their teacher am the only one with control over their ranks. However my fourth degree means that i can only test people upto fourth degree "under the guy who signed that document" meaning in that lineage.
I might ask, if i feel i am being treated unfairly by my teacher, why would i want to promote more people into his family when i can go to any streetcorner storefront school in america and find a new family that would treat me appropriately?
hope this helps.