Halcro, points are a sort of mechanical one-way diode. That is they are fairly efficient at transmitting vibration in only one direction. So if your points are pointed *down* under your tone arm: welcome to your plinth, the anti-vibration platform.
Any good anti-vibration platform will have both 'acoustically dead' and 'absolutely rigid' as a mantra.
I agree that a bad plinth is likely worse than none. I've been down this path before- my turntable has been in development since the early 1990s. So the comments I've been making are based out of experience, not conjecture.
If you want to separate something, and if the 'table is not a direct-drive, then the motor might be a better candidate. However IME the vibration of the motor will be of no significance if the plinth works right.