"Solid" and isolation are not necessarily opposing designs. I have first-hand experience with other components but have only read (a lot) to find a good design for a stand for my own turntable. The possible issue with isolation techniques you are considering is that the resonance frequency of those items may be too high, not to mention how the questionable amount of damping they have (too much or too little).
High rigidity stand/shelves will decrease the vibration amplitude prior to the resonant frequency and increase the resonance frequency - as will a low mass - which is desirable. High mass is inversely proportional to vibration amplitude above the resonant frequency, so there is a trade off.
Kuzma as an okay pdf for setup, although the information they have about mass and "stored energy" I don't think is perfectly correct: http://www.kuzma.si/media/uploads/files/Setting%20up%20a%20Turntable.pdf
High rigidity stand/shelves will decrease the vibration amplitude prior to the resonant frequency and increase the resonance frequency - as will a low mass - which is desirable. High mass is inversely proportional to vibration amplitude above the resonant frequency, so there is a trade off.
Kuzma as an okay pdf for setup, although the information they have about mass and "stored energy" I don't think is perfectly correct: http://www.kuzma.si/media/uploads/files/Setting%20up%20a%20Turntable.pdf