Nice idea.
If you're taking constructive suggestions; I'm heavily into Hugo, which is excellent for all the usual reasons. But one thing that really irritates is breaking features. Keywords being deprecated from hugo.yaml in particular. I don't constantly update my sites, so remembering where everything is can take some time.
If you were to actively resist feature bloat (as suggested by your premis) then that also lends itself to not having breaking changes. If scaff were to feature "always backwards compatible" - handling any later changes silently internally - it might wins some friends? Low maintenance, easy to learn, low effort SSG. Leave the singing and dancing to the mature frameworks.
Anyway - good luck, whether you take my thoughts on board or not!