I had half your problem (shelf above) and used the exterior filament arm but ‘upside down’ so the spool isn’t quite as high. (A250 in my case.) You can see it in the background of this pic:
I’m not sure you can just use the same hanger as-is on the right side of the machine, given that the door is intended to hinge back. I don’t know if you can essentially totally “invert” all the sides and doors so you have front and left opening not front and right…but if you didn’t have room for the spool on the left you won’t for the panel to accordian-fold out either, will you? Hm.
It looks like to me that a spool would fit INSIDE the enclosure, either mounted with axis parallel to the machine’s “Y” on the back wall, or mounted with axis parallel to the machine’s “Z” suspended from the top. The Z modules don’t move relative to the housing so there’s always the same space back there, aside from room for the heated bed cable to wiggle around during printing.
You’d have to drill holes in the enclosure and rig some sort of hub fitting, similar to how the duct port screws in and swapping filaments might be a bit more cumbersome with the chance of cables being in your way if you were working thru the side door or whatever. But the filament would be inside an (in use) warm closed area and likely a little more protected from humidity in the longer run. (Of course you might not want filament in there while lasering or definitely millling!)
Foreground of the pic above has my secondary filament hubs mounted on the same pipe that supports the shelf above - I’ve got a total of 3 spools mounted these days, one “on” the machine and two adjacent on the pipe, any 3 of which can route thru the grommet.