Letch, granite slabs are a common platform for the Teres tables, and other high-mass unsuspended tables. I have heard mostly good reports about using granite as a base with these tables. I personally do not use granite under mine, but it would be much preferred to using anything rubbery. I once experimented with some soft materials under the cone feet of my Teres. I used only very thin sheet materials, which compressed quite a bit when loaded by the weight of the TT. Even with this thin layer of springy material, the dynamics and leading edges of the music were severely blunted. When I tried thicker stuff, it got even worse. In my opinion, the results of the damping layers caused much worse results than any vibration problems that may have been there. When I returned to just the Audiopoints, then the sound returned as it was. I have only rigid materials between my TT and the floor. Interestingly, I had alot more trouble with footfalls and floorborne vibrations when I had my suspended Linn, than I do with my Teres. The Linn used to "dance around" on it's suspension all the time, even when I would tip-toe around the house. My unsuspended Teres just sits there, rock solid, and there seems to be no effect on it from walking around the house. That was a big plus for me, and I have no desire for another suspended TT again.
Regarding your Oracle situation, I was a high end dealer's analog setup guy during the 1980's. We were a Linn dealer, and also had a number of other TT lines, as well as having alot of trade-in tables around. I got alot of experience with alot of different tables, arms, and cartridges during these years. My experience was that the suspended turntables such as Linn, Oracle, and such, favored the use of a lightweight(lower mass) rigid stand with no flex. The higher mass unsuspended tables preferred heavier mass rigid stands. This apparently related to the resonant frequencies of the different types of stands, and the effects on the turntable's suspension(or lack of it). But, both preferred rigid type stands, just different mass. I also recommend using a low stand that is as low as is comfortable for you to use. A low stand has less flex or ability to move around, and also has a shorter vibration path.
Regarding the Bright Star, I've never used one, but I'd recommend getting a suitable lightweight rigid stand, and trying the TT with the Bright Star, and without it, to see which you prefer. My guess is that it would be better without it, but you should test it and see which you like.
Also, as they say "YMMV" because systems vary for resolution capability, and listener's tastes vary. Some people will prefer an "overdamped" quiet sound, over a highly dynamic sound. Generally, when you start "pushing the envelope" in dynamics and resolution, then the "warts" of the system start to show themselves more negatively. This can be irritating to some people, and they prefer to damp down the system to cover up the warts from showing. That is pretty common these days.
Ultimately, it is what you prefer that is best. I try to push the envelope as far as I can, and then attempt to correct the flaws that show up(at their sources). My budget limits me in how well I can do this, but I do what I can with the budget I have. Also, I accept certain sonic flaws in order to gain some other sonic benefits that are important to me and my sensitivities as a listener.
If you want my guess about what will happen with the GPA, I'd say that it will be a quiet presentation with very little floorborne vibration problems(they do that very well). It will also very likely sound overdamped and will have little affect on any airborne vibrations entering the system. The GPA is great for making the system quiet and "polite".
If you are looking to extend the performance envelope of the musical dynamics, resolution, PRAT, and "lifelike sound", then there are other ways which would likely yield better results in these areas.
