SoulWrangler
First off, there's the argument that, according to the version of the script(which claimed to be the final shooting script) i read, the first containment unit was half of the firehouse basement with a laser grid around it, and the wall with the input was added. the RGB containment unit contained a synthetic micro demension. the last time I checked, in terms of storage space, Micro-dimensions>half a firehouse basement. [Plus, lookit all that detail, man! how could they make the old, wall-mounted ECU look that cool?
This is six months after Gozer, and their tech isn't anywere near creating micro dimensions. I really doubt that Sebastien and Co (Sundays on Fox) are wanting to use the micro dimensions theory because that goes against the idea of the ghost prison that Aykroyd wanted. If anything a better way of explaining this massive boiler room looking structure is that the original ECU was a day spa prison, and the new version is a maximum security prison. Space was never an issue, if a large ghost could be dematerialized into a 1x2' box for temporary containment, who's to say that they can't just continually shove ghost after ghost into the system; squeezing them all together. Personally, I would've rather have seen an all new and unique design for this, but I understand their desire to please hardcore RGB fans.
Valid points(except 1), though until someone from 88mph explains how the new ECU works, there's no telling which, if either of us is right or wrong. I just figured, if they're using the RGB exterior design, they'd probably use the whole concept. However, I do have to disagree that space wasn't an issue. If space wasn't an issue, Ray probably wouldn't have said “it's getting crowded in there”. Maybe they figured out a way to get around the space issue that isn't a micro-dimension, maybe space still is an issue, we just don't know. It'd be nice if we did know, though(blatant hint to any 88mph folks reading)
edit: I hate working with multiple quote tags.