Well, you could try looking at some languages developed by non-(native-)English speakers e.g; Eiffel, Ruby, etc. Granted, they've not created them in isolation.

While no linguist, I'd have to say your last statement is way off base though, given what I have read. English has far more in common with German than the Romance languages, once you recognize that we've lifted about 2/3 of our vocabulary from Latin and the Normans; with a bit of Greek and Hebrew/Yiddish thrown in. Not that we should be looking at vocabulary anyways since your question was about grammar :-P

As for the question itself, I should think that the model chosen (OO, functional, etc.) and the limits of serial transcription of directions (writing linearly) would be the larger limitations. But then, my name isn't Minsky either.