i have been typing on ibm keyboards since 82 and hacking them for a couple of years now and i know the M and F pretty well. what you are discussing here is what i set out to do here:
http://deskthority.net/workshop-f7/bringing-the-ibm-pc-xt-into-the-21st-century-t3047.html
it is a long thread so i will sum it up like this: i was successful at rearranging the keys to my liking - similar to a TKL - but it fit back in the case of an XT. i even DIY etched a capacitive matrix and could measure capacitive changes with the XT hammers down and up. but i could not recreate a capacitive controller. heck i could not even remove and re-attach a working controller. capacitive sensing is a finicky thing.
Which is exactly what I said a couple posts back, I do believe.
And as you know and can attest to, it's not a matter of just reproducing what was there. Parts are unavailable with no cross-reference, there's proprietary elements involved, and so on. Capacitive sensing is also extremely sensitive to things like EMI/RFI, inductance and resistance. You need world class electrical engineers to put together a reliable design that's suitable for mass production. And a
lot of testing.
but i did notice that a model F with model M hammers feels like a model F; and a model M with model F hammers feels like an M. this was a big surprise to me - i always thought that the feel was from the hammers or from the PCB/membrane. now i think feel comes more from the barrel frame than anything else; the F feels the way it does because loose barrels are sandwiched between two sheets of metal. anyway, that led me to wanting to make custom membranes - which is my project now.
what i am suggesting is that it might be possible to get the feel of the F without going capacitive.
Ayup, the feel is largely from two elements - the springs and the frame. Why is this? Because these are the only two elements you're actually interacting with. The barrel frame is what defines the keycap motion, spring angle and such. The spring is well, the spring. But once the spring "buckles"? That's it. You're still only feeling the spring. It sits between you and the hammer, not to mention the membrane/PCB and frame.
But it's not all tea and roses here either. To my knowledge, all of the F tooling is long, long gone. Yes, you can get the springs and hammers. But you can't get the upper moldings - by far the most complicated element from a tooling standpoint. (The chassis uppers themselves aren't easy, but pale in comparison to the complexity of barrels and integrated hinge mounts for hammers. So many fiddly bits!) So you'd pretty much be starting from scratch, unless you could find an absolutely pristine new in box F that had been kept in a perfect environment its whole life.
So yeah, we can rule that out. Which means it comes down to the same issue as reinventing capacitive - the need for a lot of from-scratch engineering, prototyping and testing. 3D printers or not, that's still a lot of money you have to invest.
And like I say a lot, it comes down to the economies of scale. We're what, maybe a hundred to two hundred units sold? Call it 500 units throwing in with the rest of the world, maybe 750. And these are one-time sales, since if they're true to the F, they'll last 30 years. And no, you can't use a desktop 3D printer - the dimensions alone mean you're looking at a Stratasys Objet 500V (19.1" longest dimension vs. 14" for the 360V) - so you're already WELL over
$50K in the hole. Seriously, that thing's so expensive it's pricing-by-quote-only.
Dimension 1200es pricing for comparison - SST at $35K and it can't handle the required dimensions.
So I have little hope we'll see it any time soon, unfortunately. It's just too damn expensive a proposition for pretty much anyone to undertake.
