For the former the problem is as you say already technical; it is likely even worse than you describe because "we" cannot change the software (by and large). There are some details that can be modified, but this one I doubt it.
For the latter, beyon technicalities, the worry is that such things might annoy some potentially valuable contributors enough to stay away, while not really keeping away the not so valuable ones. (The real problems, IMO, are mainly not caused by those that do not know TeX.) And (La)TeX could be a problem for legitimate users; true only few but there should be some.
This is somehow an abstractly interesting idea but in practise it will unfortunately not be possible, IMO.
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