After about 400 flights on a couple of Savex L-39's (Wren 44 Gold), I felt that the Ultra Flash was a lot easier to fly than the L-39. After starting to fly the UF, the little L-39 has not left the house.
Does the little L-39 prepare you for a heavy scale jet - absolutely not, but using it as a stepping stone to something like an UF/ T1/ Havoc/ Boomerang etc. is perfectly doable.
If someone could fly the little L-39 well, I'd have no issues recommending them for a waiver (baring the 12lb rule, that is).
The waiver is just like a driving license - nothing to stop you driving a Ferrari the day after getting the license, (as long as you can afford the insurance).
You have to rely on some amount of self-policing.
Paul