OK so having given this some consideration I'm gonna try a local conversion and just try to grok how broken things are, before commiting to a specific path.
Its likely we merge the base of both projects into a 'dirty bootstrap', and reuse the D based infrastructure we created to automate rebuilding our source conversions.
At some point boulder will be Rust based along with a considerable part of the build infrastructure. However, despite the known deficiencies in the old tooling, they'll suffice to get us up and running, and we can defer those rewrites.
If we play our cards right we'll get Solus .stone'd in next to no time.