One thought I had, is that even though the SL1200 chassis is carrying much more weight with the MN platter & bearing/plate, I do not believe it is 'overloaded' or that the drive system is overtaxed.
On the contrary, I am hearing the best vinyl playback ever out of this deck, and I would bet that it rivals super high end decks.
I also have the Hynes PR3HD power supply module in a DIY PSU I built (equivalent to the SR5)
I think if there is anything to be gained, the very last smidgen of improvement might be realized with a whole new plinth, which is vastly stiffer than the SL1200 chassis. But this is only speculation on my part.
Hey... someone ought to design one

Please add provision for both 9" and 12" tonearms as well.