Hi Els,
In my view this is a clear level 3 decision, as it impacts the entire group (see also the Goverance Document, section 5.1.2), so it should definitely go to a plenary meeting.
As for the reviews of a proposal, this is covered in section 5.1.3 of the Goverance Document. The objective is to make sure the proposal is clear and understandable, so the suggestion is to ask people from outside the team. In practice we often have reviews from inside the team, which can also work in some cases.
What isn’t listed (yet) in the Governance Document, is a desire to get a view on major objections ahead of a plenary, in view of spending plenary meeting time wisely. This request to consult beforehand is currently only listed in an Edgeryders post and will probably be included in the next review of the Document (see Raising concerns and objections ahead of a plenary meeting).
When were you planning to bring this proposal to a plenary?