Publication TOC on chunked ditamap

[hugi]

Hi there,
I hope I'm not asking something that has already been answered, but I haven't found any posts on this exact matter on the forum.

I have been tasked to generate a single-page WebHelp output in addition to the standard output from a ditamap containing numerous topics.
I used the chunk attribute with the value "to-content" on the map and, in another test sample, the "root-chunk-override" argument juste to see if there would be any differences, to achieve the desired result. While I’m able to customize the whole thing with fragments, I’m stuck on the publication TOC. I’ve been asked to include the publication TOC in the single-page output, but I understand that oXygen automatically removes it from this type of output, and I'm left with the topic TOC, which only contains what is considered as sections.

So my question is: is it possible to get a standard publication TOC (starting to level 1 entries) on a single-page WebHelp output as one would have on the left of a standard WebHelp output?
I guess it would be possible by using an HTML transformation scenario, or a DITA-OT plugin, but the responsive aspect would be harder to manage.
The thing is that the solution needs to be simple enough to be easily adapted and/or modified in the future by other people, which is why I have doubts about an HTML output or adding a DITA-OT plugin, especially since we use a CCMS.

Thank you for your help.

Hugo