To follow through with my point:
to present a PREVIEW of the modified page [by] allowing Hugo templates to be more isomorphic
I see NetlifyCMS.org actually uses React to render live previews by letting developers expose their template in React language (for what I understand one developer must then implement the same template twice, in both Hugo and React).
So is there a way we could kinda GopherJS-ize Hugo templates so that they have meaning in the browser world ? This would definitely close the gap to have real Web-Based editing experience. In fact, a minimal page with vertical split windows could help non-tech users getting started : left pane with markdown file, right pane with live result, then a button
Publish that would just send the markdown content to git.
Obviously, one can think about even greater things in terms of UI/UX like extracting fields from Archtypes to create proper input fields etc… but the critical part is, from my point of view, to present a preview a la wordpress right after changing content and before broadcasting to an audience…