It sounds like you're off to a good start. I was thinking about an automotive panel dampening spray. The car stereo guys on the forum probably have favorite brands. I'm sure 3-M makes adhesive backed membranes too. Your tone arm "shock absorber" has been done before using a dust brush at one end, and attached to the tonearm on the other. A setup like that might cause the Rabco to mistrack. The option of a trough attached to the base seems much easier. I'm not a believer in fancy cables, so no opinions there. I wonder if there's a way to eliminate the wire to wire motor contact switch. That is a problem area. Gold plated contacts, or an optical sensor?
Please post some pics as you progress.

Take care,

Steve