Using a commercial Escrow service would work. The compny providing the training would be able to make arrangements with their bank for facilities based on the safe knowledge that the fee's would be secure in Escrow.
The student would be protected against the demise of a company (such as Cabair) payments to the supplier could be triggered by key performance achievements (Exams taken, hours flown, ratings issued etc). The money would be held securely by an independent third party company protecting both supplier and student.
So the obvious question, cost? For such an arrangement normally 3 - 10% of the total value. Yes, it would add a cost to the course, but in my mind that cost should be regarded as insurance by the student against loosing all the money paid up front.
There are more obvious questions like how can the CAA issue a TRTO to a dormant company? If you read CAA Standards document 34, then that should not be possible. Recently it came to light that is exactly what happened with another company (not Cabair). In its own standards document the CAA talk of minimum financial requirements for a company, yet it clearly made a huge mistake by issuing a TRTO to a dormant company.