The physical size of the craft can be gauged buy the physical size of the bridge interior, compared to the external shots. This clearly makes it smaller than a Whitestar. Also, in "Sleeping In Light", one was able to dock with Babylon 5, something which the Whitestars were too big for. The model clearly shows a pair of weapons on the front of the engine pylons, so that would indicate that it has some combat capabilities. Had it been just a transport, they'd probably have given it a defensive turret or something. As for the nose gun... well, that was my idea. It seemed that for our purposes, the pulse guns seemed a bit limited in armament, so rather than creating another whole class of beam weapon for the nose, I decided to use the Nial's neutron gun in a cycling set of firepoints.