BuddyPress.org

Thanks for your explanation @themeanwhile

“have you heard of anyone else trying this?”
Bring front end applications to backend – No.
It’s the other way around – bring everything from the backend to the front end so that users won’t need to access the back end at all especially where BP is installed.e.g. writing posts in front end via BP/Jet Quickpress, uploading media in front end via BP Gallery/Album, adding events in front via Event plugin etc. Therefore, yes as you noted at the beginning, you would need a BuddyPress wiz to create a plugin which will enable you to have the specs you want for the Activity part.