At least you'll have the option of moving on to CPL instruction and possibly IR should you wish later on in your career.
Exactly!
To now, open up the back door and let any T,D or H, do it, just doesnt seem fair to me
It's not open to any T,D or H! You'd still have to pass the FIR and as PPL's are often far more experienced than CPL's these days, that is rather insulting to PPL's generally!
If you really wanted to be selective, you'd select potential FIR's by flying experience, teaching experience and aptitude. Certainly, just the fact that they have a CPL (which to be blunt is little reflection of skill or experience) means nothing about their ability to teach flying skills at PPL level. To be fair, the CPL is a reasonable measure of "standard", but that could easily be measured without the need to become a CPL.
SS