Sorry, that is simply not correct. When it was open (it's not currently), the CDG lounge was NOT open to all oneworld elites (i.e. those flying economy). It required a business or first class ticket, same as SIN.

Source (Qatar's own landing page for the lounge): https://www.qatarairways.com/en-us/l...um-lounge.html (see "Visiting us soon?" section) They literally call it "Premium Lounge"

And the LHR lounge is exactly the same criteria and it only has two flights per day.

So again, my point is that though I don't know what the Oneworld Lounge plan for FRA is going forward (and it seems you don't either) I suspect it has very little to do with how many flights per day QR has out of FRA. If QR wants a premium lounge they'll make it a premium lounge and if OneWorld wants a generic OneWorld lounge for all OW elites and they want QR to manage it, then they will compensate QR to do that.

Regards