More generally, I would like to contribute back some of the custom library elements that we use, when those might be of interest to a larger audience, but I currently lack the resources to submit proper patches (project is late). Would it be acceptable to drop the occasional element in here for anyone who has the opportunity to eventually patch it in?
No, and we don’t even take patches. If you want your asset to be included then you MUST open a pull request on github, PROVIDE all required additional documentation and fix anything we request to be fixed. Your screenshot for example already violates at least 4 KLC rules. (no courtyard, rotated wrong, silkscreen to close to pad, missing reference on fab)