"Valet" and "cadet" is an interesting pair: they rhyme in French (/va.lɛ/ and /ka.dɛ/), but rhyming them in English would be ... unusual.

If there were just French words pronounced in a French way and English words which came from French and are now pronounced in an English way that would be bad enough but in fact we have a whole spectrum of bastardisation.

Interestingly in British english valet would rhyme with cadet if you were referring to a servant and not to someone who will park your car.