I'm just gunna throw this out there: The replacement for the axidraw 8.5x11 thing is $699 - a fully loaded cricut maker 3 is $429, and can, in theory, do actual plotting on sheets longer than 11" - as well as being a vinyl cutting machine. I am unsure what models of cricut can take the pen holder, but it is something to consider, especially since i am sure there are alternatives to the ecosystem that are more open or support different software.
Also the ender series of 3d printers can make use of a pen attachment as well, but those are 8x8 inches. There are larger 3d printers, and the software or whatever to plot with the ender 3 was open source enough. My ender3 was <$200