I like the filament on rods, but only for open packages. Most filament ships airtight and can't be put on a rod without breaking the seal. (Plastics do degrade/deform when exposed to moisture long term.)
I suggest a few rods for spools that are already open. Doubt we'd need them locked since it'll be community plastic anyway. Sellable plastic will need another storage solution but should probably be organized under the table somehow.
The half-cut PVC won't keep the in-use spools secure and will easily fall over/off or be cumbersome. The machine's current spool holders are fine for v1 of the table.
8 feet wide table will consume half of the space we currently have for the chairs. Our current table footprint is 6'x2.5'. This surface could easily accommodate three printers side-by-side. If anything, I would keep the same footprint, raise it 6", and eventually add a small screen for monitoring prints.
The computer that's there should be moved over to the computers along the back of the wall once we get the PrintrBot (and eventually Ulti) connected to a Raspi running some printer manager. The printer manager should/will drive the small display screen.
For the sellable plastic, how about a drawer at the top of the table that shows the colors with a lid that let's the colors show through the top?