You can make another station to load that one wagon if you want. However, the PAX system is just a L-C-L train mainly just to get around yourself. Regarding the PAX, see the first post above with links and details. Please send me the changes you have made to the science so I can include that changes maybe in future? Anyone else is welcome to help out and send me their ideas and changes. (At nights I lay awake thinking how to fit an assembler in there to make exo suits.) So in due time I will still fiddle around with it. I do plan to change my mall around when Factorio gets released to make that much awaited Spidertron and any other things I can add. The current version of the mall on my PC have a roboport moved and an assembler in there to make the refined hazard concrete.

I have something like that in the back of my mind. No, unfortunately I couldn't fit an assembler in there to make the standalone artileries.However, iirc, the wagon arty assembler can just be manually changed to produce the standalone ones.