I fear this thread could just run and run, but to summarise:
I think that accreditation and completion of, and graduation from, a recognised school and course should be mandatory for TPs/FTEs involved in aircraft test and evaluation where there is a safety concern. There should be a minimum criteria for such a course, which focusses deals with risk assessment and mitigation.
Just because the rules say that a nurse can do the job that a highly trained doctor usually does, I wouldn't want a nurse performing open heart surgery on me, regardless of how many times she'd seen a qualified doctor do it, or how long she'd stood in theatre. I'd go for the newly-qualified doctor every time. I wouldn't let a sectetary represent me in a complicated fraud case, regardless of how many times she'd filed some legal paperwork; I'd always take a proper brief.
A TP without TPS accreditation is just a pilot, an FTE just an Engineer (although you don't even need ANY qualifications to call yourself an engineer. I told my nan this, and she's just applied for a job at BAEs as an FTE).