Maybe this worth a look too: "Custom theme for our two Discourse
sites". [1]
Please get in touch with the design team (aka, lurk and eventually
reply to the linked ticket) if you think you have the necessary skills,
or if you are interested in the issue.
I think that, probably, this request needs various disussions and
coordination, and not simply to execute a task.
[1]
https://pagure.io/design/issue/704
Ciao,
A.