Ah yes, I knew I was thinking of another aspect when I decided to originally post. Yes, I do STRONGLY believe that a minimum range is in order. On careful consideration I believe that it can not actively fire at anything closer than 3-4 spaces, or maybe the current RG range. Do to the area effect and spread fire natures of this unit, one could force target at the innermost edge of the minimum distance and nearly hit a target just inside of this zone with perhaps 10-15% of its rounds. This would more or less be useless though as if a combat unit got this close, the physical weakness of the unit wouldn't survive long enough to kill the attacker and be of any further use. You don't see howitzers and MLRS units on the front lines of more modern battles. Why? Because they are fairly weak units that would get their asses handed to them by even light infantry.
I wouldn't view them as "Extreme Long Range" weapons. Another spec I forgot to add would be maximum range. My personal thoughts on the topic would be in the area of 15-20 spaces which is 2/3s or less of a screen height or roughly a 1/2 screen width on my computer. (my screen shows 42, 34 of the battle field)
As for a Chasis maybe a lightly modified ConVec base? It is about the right shape and size. The research tech could say they modifed a ConVec to carry the weapon, which is very plausible from several aspects:
A: In the story of OP2, when Axen borrows/tests the Thor's Hammer Tiger, he sees the rebel base has several "strange" combat units. Most are Lynx' with extra weapons and armor welded to the sides, but he does see, and I (roughly) quote, "a ConVec with a guardpost turret welded to the top".
B: The ConVec manipulator arm could be used as a structural base for supporting the turret and would allow the turret to be swiveled and tilted using the existing actuators, which would also have to be upgraded in the initial tech to be able to move and support the massive turret. Thus lengthening the initial research tech time.
Diagram showing the difference between MLRS tragectories vs the EMP Missile tragectory:
http://tdg.freeshell.org/pictures/MPMLRS%20VS%20EMP.PNG Yes, I REALLY get into my MSPaint drawings. Not bad for a crappy touchpad for a mouse
This drawing is mainly directed towards Sirbomber and Freeza, as well as anybody else who might need clarification.
Brian.