For those not wanting a touch screen for MacOS, we do have a Surface (1.... it's a typical version 1 device) that does have a touch screen, and here's the thing: You can use a mouse with it, so it's a win-win. Don't want to use a mouse? Use the touch screen. Want to use a mouse? Use a mouse. I think it's the capability to use these devices with an iPad, not the mandatory requirement to do so.
As for macOS on an iPad, that's a tricky one. macOS already has a touch interface, the trackpad, so to integrate that into the screen shouldn't be totally out of this world. I bet that
already has computers/iPads in house doing this, but the user experience may be hard to sell to the higher ups. However, that new program that lets you use the iPad as a screen/pencil input, if it takes hold, may convince them, if enough people buy it. That would be a crude version of macOS on an iPad.
The iPad Pro has two connectors now, and the smart connector has a lot of potential, especially for attached peripherals, but then again, the three pin connection only allows for serial communication, and it would have to be multiplexed should a smarter keyboard, with ports and such be invented (keyboard with USB, video, storage). I think that the storage/USB/video would be the bottleneck, but Thunderbolt seems to pull it off, but with more pins/channels.
And yes, punch card readers do exist for the Mac. Making it work for the iPad needs to be done too...