So, I was on the wiki looking through the new LM's, I saw quite a few differences between the old and the new ones, and I was wondering, what's the next step?
I would suggest Inter-Legional Missions.
New Legion missions that require multiple legions to join them, through Mission Pacts. They would take up the Legion Mission slot and timer.
The timers could be pretty tricky, but I believe it is doable.
Anyone have any thoughts on the concept?

Difficult to implement as you suggest, unless it was a separate mechanic entirely.

Also, we would have to bare in mind the costs. As it stands, there aren't many legions that can garner success with their own LM's due to lacking the capability(through no fault of their own) to sometimes even complete a task, adding in a new set of tasks/missions that take up more of their energy, well suffice to say, it's probably a year maybe even 2 years from being a good idea to introduce something else that might cost more energy.

It is interesting. With Mission Pact, you can invite your legion to join in a mission - much like a base invitation, or elite/boss NPC alert. One thing to consider is that the mission should only be shareable in the first day of the legion mission, to prevent something like 12-bases-a-day-battle-group.

The mission itself should only get 1 day timer - but that will require a LOT of iLM variety, and that means more work for Dan - so maybe 2 days is reasonable.

Due to the lack of ease of communication between the legions, I would say this is a bad idea right now. However, if something like a better comm system were implemented, then I'd be all for it. It's a nice idea.