Figuring out what the freight shed is going to look like

Now that the Emsingen station building is basically complete, I need to figure out what the freight shed is going to look like. This will be kit-bashed from parts of the attached freight shed included with the kit, and styrene sheets. Do I want two doors to the loading platform or one? Which wall segments will be built from kit parts, which from styrene parts? Do I want to build the shed to the size of roof parts I have? If bigger, should I cobble together the roof from cut parts, or build a roof from scratch?
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So many questions to answer.

Before cutting styrene I should make a cardboard mockup.