I really like Epic: Armageddon for several reasons, and one of them is because, prior to its release, I was able to sit down in a bar with Jervis Johnson at one of the Canadian Grand Tournaments and discuss Epic 40,000 and why it flopped. The interesting thing is, of course, that Epic: Armageddon is essentially the same game as Epic 40,000 with a different, Warhammer 40,000 5th edition vibe. In particular I like the way that these systems handled what had previously, in Space Marine 2nd edition and Titan Legions, been more purely a matter of close combat using as 'caf' or Close Assault Factor. These were, of course, engagements deriving from Engage actions, and roughly mirrored the events of a game of Warhammer 40,000 when one detachment attacks another.
The neat thing, I thought, was that models had two numbers, a close-combat value and a firefight value, and that in base contact they could use the close-combat value, and within 15cm the firefight value. Which meant that shooting-oriented units, and short-ranged shooting (including defensive shooting) was subsumed into the event. In addition, friendly detachments with units within 15cm could lend a hand, meaning small detachments of Space Marines could encircle a large detachment of Orks and proceed to murder it at minimal risk to the Space Marines if anything went pear-shaped, because the supporting units did so incidentally and absorbed none of the risk of engaging.
The 5th edition of Warhammer 40,000 applied several concepts first published in Epic: Armageddon, and in particular its method for handling casualties which was later abandoned in the 6th edition: allowing players to choose casualties from within the models in the unit, or units within the detachment. Now, I can see why this would happen, given the 5th edition phenomena of the 'conga-line' of Orks following a Nob and whatnot, but it worked very well with the Epic notion of specific anti-infantry, anti-aircraft, and anti-tank weapons, and the notion of plumping out detachments with their own internal expendables, like Gretchin in Ork detachments.
I do like the notion of units interacting with units, however, and the recent inclusion of Supporting Fire as a rule for the Tau Empire in Warhammer 40,000 feels like a good idea about how little separates the Epic from the Heroic scale of game. What I think would be neat would be having a squad or detachment based system work relationally, as in one unit addresses another with other, third-party units affecting the outcome depending on proximity and so on. Movement, for example, would be towards the enemy, with models capable of getting into base contact being able to engage in close quarters combat, and models further away being required to use ranged attacks, and then a set of outcomes such as win, lose, or draw.
I would like to see a Warhammer 40,000-style of game that uses this sort of game-play to encourage a more top-down style of play, rather than the bottom-up (where the bottom is the actions of individual models, as opposed to the actions of actions) skirmish-style of play.