If I choose to issue a DRAFT RFP without legal review is that permissible under Regulation if I am Clearance Authority and make that choice to do so?
The policy and threshold for legal review of the request for proposal (RFP) and other documentation required for business clearance is set by local policy and procedures. DFARS is silent to the specific documentation that is required for business clearance. DFARS PGI 215.406-3 -- Documenting the negotiation -- primarily discusses the requirement for uploading approved pre- and post-negotiation noncompetitive business clearance documents to the Contract Business Analysis Repository (CBAR), but doesn't give specifics about what documentation needs to be in the file and who signs it. It simply states that "business clearance documents uploaded to CBAR shall be signed by the contracting officer and shall include all other signatures required by local policy/procedure."
The AFFARS, however, does have some specific guidance on clearances and legal review thresholds. AFFARS 5301.9001 -- Policy, Thresholds, and Approvals -- states the Clearance Approval Authority (CAA) is responsible for ensuring "negotiations and contract actions are consistent with laws, regulations, and policies..." The AFFARS also makes clear that "the CAA must seek legal advice (see 5301.602-2(c)(i)) and ensure that counsel has coordinated on any clearance briefings or presentations, and that counsel’s comments are included in the briefing or presentation." AFFARS 5301.602-2(c)(i) states that "contracting officers must obtain legal advice during all phases of acquisitions..." and "exercise good judgment in seeking legal reviews." As you pointed out, the threshold is $5M for legal review of non-operational contracting actions. AFFARS 5301.602-2(c)(i)(C)(1) requires legal reviews of "solicitations" for contract actions over $5M; it does not distinguish between draft and final solicitations.
Bottom line: the way I read "solicitations" is that the requirement applies to any solicitation over $5M, not only final solicitations. In order to ensure the RFP complies with laws, regulations and policies, I would consider a review of the draft RFP a prudent step given that the "draft" will become a final RFP and a preliminary legal review of the draft RFP might help ensure the review of the final RFP goes quicker. If you would rather not get a legal review of the draft RFP, you could discuss it with your legal advisor and the policy folks at higher headquarters to get their perspective on it as well.