Comment by uberduper

My take is that an RFC should be very early in the engineering process, like as part of a proof of concept phase, and should not block progress towards completing a design proposal. The design proposal should list any legitimate alternatives to overall or component designs discussed during RFC along with the reasoning for not using them in a "designs not chosen" appendix. This at least gives your engineering leadership an opportunity to evaluate the general design ideas before anyone is prepared to die on the hill of those ideas.

Architecture / Design review happens post proof of concept but still before any significant development work and major action items are blockers to beginning development. Further discussion about designs not chosen can happen here, especially when a flaw is uncovered that would be addressed by one of those not chosen.