My own level of expertise as regards the EU of Star Wars is rather limited- i'm only just reading Heir To The Empire now. However the web has alot of helpful technical and storyline resources including Saxton's pages, Thelardbiscuit and of course Wookiepedia. I have been doing alot of reading of the complete ICS and visual dictionaries also, and nowhere have I been able to find any reason why a capital ship like the Malevolence would require a huge, complex internal monorail system. Apart from the obvious "we needed an action scene", It baffles me why you would weaken a battleship's structure with a massive empty space like that. What are all those trains supposed to carry? Droid janitors? After a few days (yes I was bored
) i've come to the conclusion that maybe the monorail isn't as implausible as I believed; The Malevolence is for all intents and purposes the Seperatist flagship- she's certainly the biggest they've got and seems much bigger than anything the Republic can throw at her. Her huge size is a result of the Ion cannon technology which requires an equally huge and perhaps speciality tech reactor- i'm inclined to believe that this reactor is placed right between the two Ion "dishes" either side of the hull. This location would make sense as far as improving power distribution efficiency to these weapons plus all those hundreds of turbolasers on the bow. However, what about the ship's engines and hyperdrive? Not sure where the latter is located but for the former a huge, straight network of power feeds would be needed from the reactor to the stern- the large monorail corridor would provide the solution, provided the power conduits were located at the bottom, out of our sightlines in the cartoon. Even if the reactor IS at the back then huge conduits are required for all those weapons and especially the Ion dishes.
As flagship, the Malevolence must obviously be equipped for command-and-control: she can probably take the entire separatist leadership onboard in confort and security- this makes sense as regards the ship's highly fenestrated bow, which probably houses full living quarters for thousands of sentients- droids do not need such a lavish provision of windows. Although as a Battleship such an area represents a weakness these areas are extremely dense with weapons: http://www.bwafer.com/starwars/malevolence.html This would render them practically invulnerable to attack. For Palpatine's shady reasons these zones should be well separated from the command areas and indeed those are located right at the stern atop a fin. The monorail would provide rapid convenient transport betwen these locations which are seperated by several kilometres and if needs be the system can be deactivated and the living quarters effectively isolated from the bridge.
As command ship there will need to be a plethora of communications aerials and dishes and some are visible atop the bow sections- including several masts which may be retractable in battle- aswell as the two huge bulbous devices protruding from each side of the vessel, which may be high-powered communications devices, rendering the control of entire droid armies half a Galaxy away possible as necessary. Examining the ship one can see that most of the hull is smooth, un-greebled metal, probably meaning it is very, very thick armour which would both protect the ship and serve a structural role as the physical backbone of the vessel (aswell as a nice perch for Vulture droids) -rendering a cavernous hollow interior more viable. Other advantages of a smooth hull include less chance of damage when cruising through fields of Asteroids and Nebulae (befitting the clandestine nature of the ship's missions) and a level combat ground to repel boarders (see the Clone wars episode here at 3:15- ignore the obnoxious soundtrack
http://www.youtube.com/watch?v=yLWh49bj ... re=related ) The monorail tunnel could also function as a giant, protected heatsink for the ship's powerful shielding systems. There's my first tirade over
Realistically the tunnel would have been depressurized and the scenes which took place there would be substituted for Anakin and chums gasping fro breath, lol droids don't need air to survive.