If you have no idea where to begin the development due to lack of knowledge on the context or you're less confident on the current technical proposal, it might be better to work on Proof-of-Concept MR (PoC or Prototype) at first. This gives you more insights on the current implementation details and potential required changes.
This step removes a lot of "if"s from your assumptions. When you're making a technical proposal, often you don't have enough time to investigate the actual implementation details. In such case, you're assuming like "Probably, this feature works like …" or "Probably, this feature and that feature are connected like …", which leaves some probability in your development plan, and if it turned out a wrong assumption, you may need to rethink the whole approach, even though you're at the middle of development cycle. PoC step de-risks such a turnaround by cross-checking the technical proposal with domain/performance/security experts and UX/PM.
Technically, if you've done a PoC step, there is no need to ask for additional reviews in actual MRs as long as you don't change the feature behavior. You can simply focus on general engineering review or documentation review, only. For example, improving code quality, refactoring code, writing tests, writing documents, etc.