To my knowledge, they've never really updated the endeavor list.
Difficult ones are a pain but not bad, per se. But there are some that are disruptive. I'm thinking of Dewan Arthropods and Gorn making it hard to actually run missions on Nimbus III - I'd maybe remove the 120 Arthropods tier from that at least, and expand Gorn to include non-Nimbus mobs.
I'd also add in more variety on the TFO objectives. We only get Borg, Iconian, Lukari and Competitive. It would be nice to have some of the other groups in rotation for variety. Likewise more enemy factions on the hit list.
It might also be fun to have a top tier option to complete a mission from a certain arc that doesn't get replayed much.
They've never been consistent in how stardates work and only really just try to make sure they run in a chronological (if inconsistent) order. I'd wave off exact translations of stardates for this reason.
But also allow for human error. I know an event which miscalculated how long they've been running based on failing to understand how anniversaries work, and thus have put out a whole lot of material stating they started running a year earlier than they actually did. They could have checked the archives, but didn't.
Given how Trek is about the human condition, I think character's messing up basic facts is as good a canon fix as "The Doctor lies" is for Dr Who.