I've never tried a custom rack, but I can say they have been pretty accommodating with regards to customized caging, so I would imagine they would do the same for a rack.
They do have a standard rack they make (you have to ask for it though I think) with quite sizable tubs, known as VE-175 rack or christmas tree tub rack.
If you want the inset deli cup, you can order tubs from ARS and then have animal plastics make you a rack to fit them if you want plastic instead of the typical ARS metal. You'd just ask for the ARS 8507 tubs separately with the deli cup feature. From freedom breeder, I would go with the FB-90 w/ cup option if that is your preferred route. The FB-90W is the same tub, but with a window. This tub size is about 75% of the popular T-8 enclosure animal plastics makes and many use for ball pythons.