For community events, enable players to select a Chapter they're ''fighting for'

It would certainly give a sense which chapters are most popular and influential amongst the Pros player base--perhaps having a chapter selector on the Pros site itself to put your playthroughs towards.

I would make it about completing missions in general, that way you can quickplay into the event with any mission rather than ending up doing the same exact mission ten times in a row to prevent it from growing stale, or being held back by a player who just isn't going on that mission, thereby causing you--and by extension your favourite chapter--to underperform.

Maybe the reward would be chapter-themed items graded by how well the chapter performs--the better they do compared to the others, the more and better cosmetics they get.

[EDIT] Here's how I imagine it:

Select your chapter:

*Yes, the exorcists are technically considered an Imperial Fists successor chapter. A lot of people in the community thought they were Grey-Knights successors, which apparently even made its way into official lore about how the Exorcists view themselves. I find it very weird that even common battle brothers are allowed to so much as know of the Grey Knights no problem, and the 1st company hides the horrifying secret that they're actually descended from... The Imperial Fists!... The single most mundane chapter secret in the entire setting

**Yes, the Storm Giants are in fact confirmed Salamanders successors contrary to what the "Unknown Foundings" menu would suggest

Each one gets a roadmap of 12 items with those higher up the list being of higher quality. So first place winning all twelve of their items, 2nd place only getting 11, 3rd place getting 10, and so on, until 12th place gets just one item. Based on my math, that would result in 78 items in total. That's just with my layout, though, and it's hardly final. Let's say they only use the First-Founding layout of 9 chapters. That would mean a roadmap of 9 items per chapter, with 1st place getting all 9, and 9th place getting only 1, which would equal out to 45 items implemented total. Still a lot, but more feasible.

This kind of event would also essentially act as a popularity poll.