While the internal 21V regulator is quite sufficient, the 5V and the 9.4V are not.
Replacing them with better regulators is a good idea.
Even with the high quality Paul Hynes regulators, that doesn't cost an arm and a leg...
Another thing, if you make the effort of putting the transformer in a different housing, it might be a good idea to include a rectifier and a "large" capacitor (let's say 4700µF), feeding the TT witn DC.
You're mentioning 1A, in reality, the current draw of the Technics is around 300mA.
not a problem for a microphone cable...
(not that I believe it's usefull to shield those "power" cables, I believe it's wiser to install a small HF filter inside the TT)
Technics SL-1200 Mk2 recapped / MN bearing / Funk Firm Platter / Denon 103R / Lundahl LL1681
Thorens TD 126 MkIII / SME Series III / Ortofon SME 30H // AT-OC9ML/II
Thorens TD 160 / TP16 / Stanton 681SE
Denon DP-1200 - WIP -