I'm very interested in looking at creating tools to help developers maintain and upgrade their own custom plugins to new versions of Moodle.
In particular, I've been looking at Rector for automating plugin upgrades, and PHPStan (which Rector uses under the hood) for finding issues. I have a couple of proof-of-concept plugins for these tools for Moodle (rector-moodle and phpstan-moodle) but would be keen use the time at the DevCamp to create useful production-ready tools.
If anyone is interested in this side of things I'd be very keen to collaborate. I appreciate that, unlike most of the proposals here, it's not actual Moodle functionality, but I hope it is in the spirit of the thing!