The "English creole" hypothesis has been discussed a lot and it is true that English is a bit special within Europe in having absorbed a lot of material from other languages such as French and Norse, but I still think that it is very recognisable as a Germanic language (both grammatically as well as from the perspective of "core vocabulary"), so I don't think that the languages "merged" in the same way as this maybe happened in the case of some recognised creoles. (See e.g. here for a summary: https://en.m.wikipedia.org/wiki/Middle_English_creole_hypoth...)

There is still no reason in principle why English couldn't have chosen a more regular system of spelling, especially at a time where literacy was low anyway. The idea that the spelling is irregular because you have several competing systems (French vs. Anglo-Saxon vs. Norse) might sound compelling, but I don't think it holds water, cf. homographs such as "sow" (female pig) and "sow" (to plant) which both have Old English origins.

(Also I don't think that "rendez-vous" is a good example. I don't have hard evidence, but I would find it entirely implausible that this is a word of Norman origin, it's much more likely to be a late import from the 18th or 19th century, when French was fashionable, not at all comparable to something like "pork".)