I don't believe the "occurs on fairly regular basis" is correct. There are times where we add additional modes by community request or concern, but overall that is rather rare. I think it's needed to happen maybe 4 or 5 times in the past year, and I'm not sure it's needed to happen at all across the past several months?
One of the more recurring issues last year was the lack of Co-Op Compatibility. That means a mission chain might require Achievements and be a hard blocker for a Co-Op Only player, or may not even have the mode listed at all which would also be exclusionary. As a response for our large Co-Op main population on NA, I personally check each update prior to release with a Co-Op Compatibility Review. Basically, "Can this be done in Co-Op?". Main and Side Events need to have a path to completion which is typically a grind path for an achievable reward as Co-Op is more conducive to grinds as opposed to "one-shots"/"challenges" ("In a single battle, do X"). Where challenges exist, an Or condition providing a Co-Op grind path exists unless the challenge is completely optional (like the last mission in a weekly dockyard chain that is not needed to complete the week).
The only outlier which has existed since then have been the Supership Supporting missions, which are Random Battle only because they directly exist to increase Random Battle Participation with Superships (because the Service Cost is prohibitive). They function on a basic level as a resource exchange as they change Credits into Research Points or Coal or Steel, but they primarily exist for queue time comfort.
The Operations mode has seen a revival since Random Operations were released in 0.11.8, and players have started requesting them to be included in more of the types of grinds. Some grinds are not conducive to use of the mode, because the amount of Damage or Kills which can be consistently hoovered up in Operations is simply massive. Others could likely be bumped to bizarre levels with some organized play that uses the operation in non-intended ways. However, Base XP and Free XP look to be compatible with the mode as they were both active for the Matilda Kelly chains so I will be aware of that for the future and can include those grind-types in my checks.
The mission is completable as written (Co-Op Compatible). Others, including Co-Op Mains, have been able to complete the chain already as it's been out for over 20 days.
Use of Boosters yields additional resources whether there is an external combat mission or not. External missions can add value to the use of them, but the missions are optional and it's up to the player in how they choose to interact with them. Some skip the content if they aren't interested in the rewards or the time investment, which is perfectly normal as everyone has different levels of engagement.
Earlier in the thread it was mentioned that the 42k section can be completed in about 80 battles (4-5 hours of Co-Op grind) with Green Bonuses or about 1/4th that time with use of Blue Bonuses. Blue Bonuses are distributed for free via our Battle Pass's free track and other in-game activities, so it can certainly be helpful to keep some for rainy days such as long or intense grinds that yield cool rewards you are particularly interested in.