Dedicated Stand for a Turntable ? Opinions.

Thank You for your responses.
Really appreciated it. All posts are very interesting. I looked in your systems ( just out of curiosity ) and I have to say all systems look awesome.
In your opinion, what is more important: mass or combination of different materials and techniques.

My first table in the mid '70s was an Ariston I suspended from the ceiling by four engine starter cords (no stretch) and turnbuckles to a double layer spruce ply shelf. Then for years I spun an LP12 on a stock Sound Org. wall stand with its light MDF shelf. As long as I caught the studs it worked beautifully with no mechanical or acoustical vibration. Now I have a 75 lb. Final Tool MkII resting on a RixRax Maple sandbox on a RixRax 2-level stand. Total mass under the 75 lb. table estimated at 200 lbs. It sits on a concrete floor and again, no vibration problems whatsoever. What I've learned is that it depends on the type of deck (suspended vs. high mass unsuspended) and type of flooring (sprung vs. unsprung).

apollo wall moount

Listening room is on the top floor with a springy floors.
I don't think my walls are a good candidate for a wall mount neither. Lenco in new plinth will weight about 65 pounds and isolation platform with two phono arm towers will be about 35 pounds.
I am thinking - steel lags, fill-able with sand or other media.
Top and shelves from a sandwich of 3/4inch birch ply, Baltic ply, solid wood and MDF
Can't figure out the best way to connect shelves and top to the support lags. I can have lags fabricated with 3 cross sections at different heights then mount cones with sharp tip facing up and setting shelves on top of them.
Just an idea.

Springy floors are tough. Maybe you should look at getting the spring out of the floor. Some more support between the joists, perhaps?