Artisan Fidelity beside restoration of 301s offer a newly manufactured top plate made from milled aluminum billet with a more robust bearing mount, etc. I would think that this would be a large improvement. They have been available for a few years though I am not aware of any review or reports as of yet.
I could be wrong, but I suspect AF sources the chassis you mention from Ray at Classic HiFi in the UK who actually has them custom made by a machine shop vendor in the UK. But that said, what does any of that have to do with whether or not SME is finally about to launch a new Garrard now that they bought the rights? There are lots of third parties who make modified parts for Thorens TD124's and Garrard 301's for the simple reason that both tables have legions of cult fans and there were a huge number of TD124's and 301's manufactured and those that have not been snapped up often need work to bring them up to top performance which then prompts the buyer to think about modifications. For both decks there are third party outfits that produce plinths, idler wheels, bushings, platters, platter bearings, motor brushes, motor mount springs, rubber grommets, and all kinds of things the Brits quaintly call "the bits".