I think a lot left-handed keypad designs get marginalized because there is an assumption that they are only of interested to the left-handed user.
"marginalized"? I've never even heard of a left handed keypad design on GH. I can only find two designs when I google search. Just because something is extremely niche/unpopular doesn't mean someones trying to "keep it down"
)
With that being said, a stand alone numberpad could easily be made dual sided - like the Lets Split or Ergodox. But it's probably easier to just add the 3 missing key positions (for the 2u caps) on the normal facing side. You can this being done already on this GHpad where a full 1u layout is supported, you'd just need to mirror the 'extra' positions of the 2u keys
https://geekhack.org/index.php?topic=38963.0Having a full size keyboard PCB reversable doesn't make any sense unless it's symertrical (which a RS96 isn't). If you flipped the RS96 plate you'd have to put Esc,Tab,Capslock on the Right side of your board... If that's what you want then I'd suggest hand wiring and posting some pictures!
Someone please correct me if totally flipped keyboard layouts exist