Yes, exactly. Our community has a 52 in 52 challenge where there’s a weekly challenge for a year, so non-daily checkins would give more flexibility for different kinds of challenges.
Discourse Calendar (and Event) allows admin to set the week starting on Saturday, Sunday, or Monday, so if you want to plan for compatibility with that plugin down the road (like generating calendar events for checkins or start/end date?) I might follow how Calendar sets the week? For my community specifically I don’t think it matters.
Category mods in addition to regular mods would be really great – we have little interest groups that have their own sub categories, and it would be nice to allow those category mods to run separate challenges without making them full mods.