Another crazy notion: build a laptop style keyboard which (with the original keyboard removed of course) sits right on top of the portions of the case surrounding the original keyboard, and has consequent key height slightly less than the conventional keyboard (due to much lower key height on the replacement board).
Doesn't offer the same tactile advantages as good modern desktop keyboard mechanisms, but I'd still prefer a nice modern laptop-style keyboard to my hugely worn out and mushy TI 99/4A mechanisms.
But more importantly (from the point of view of the outcome being interesting), it offers a lot more real estate in which to screw around with the key layout and add keys (mainly, the prospect of a sixth row), without damaging the unit.
So like this sort of placement, but with TI-appropriate keys and key arrangement:
Downside would surely be that sourcing DIY desktop keyboard parts is easy, while repurposing or sourcing laptop mechanisms is likely to be more of a nuisance.
I was about to tell arcadeshopper "hold my beer" while I dremeled out a 4A case to fit a scrapped Dell laptop keyboard, but, you made the point right there.
Not as much fun as making a PCB though.
I use laptop style keyboards exclusively around here (IceKey and MacBookPro mostly)
Edited by FarmerPotato, Wed Jan 9, 2019 1:33 AM.