Looking at the UI today, I had a thought I will hazard to suggest.
I'd simplify the tab structure into 3 tabs (order of listed arena intended):
1. Premium
*Melee [Note: shortened name. Cleaner. "Open" suggested f2p. ]
*Axis vs Allied
*Special Events 1
*Special Events 2
2. Free-to-Play
*Training Arena
*Match Play
*World War I
*Steal the Sheep [Note: Do we need this?]
*AI Arena [Note: This has indented sub arena list like the Mission Arena does. Also don't show player count on these or maybe include active agents. Different than player v player.]
-WWI: Western Front
-WWII: Eastern Front
-WWII: Pacific
-etc
*Custom Arena [Note: This has indented sub arena list like the Mission Arena does. ]
-CptTrip's Playhouse
-POTW: Pig Pen
-etc
3. All [Note: a listing of all arena. Column headers should be clickable to sort by that criteria.]
I think for a player, this organization would be more meaningful and simple. Especially trial members, it makes it more obvious where the free-2-play stuff is.
Mission Arena? I could write an essay. Executive summary: I just done't see a path to success for this. I wish I did. The UI workflow is just too complex for your average knuckle-head and there is too much waiting overhead and you'd need an cadre of content providers to fill it.
Personally, I think the better use for the mission system are AI-Augmented arena. Players can jump in and simply take off and fight the AI that are in the air. They don't have to be a system admin to set it up, and they don't have to waste their valuable gaming time waiting around for something to start.
$0.02,
CptTrips