Allowing contributions only from big tech companies sounds ideologically questionable from free/libre software movement perspective, and it emboldens decisions which go against the user's interests, such as removing manifestv2 in Chromium.
Presumably you would still allow individual contributions but with restrictions unless someone has vouched for them or some other gating factor.
Where does the frog stop getting boiled?
Big corp accounts are pre-vouched. And it will be mostly their responsibility to vouch for other accounts.