It seemed like a great idea in 2001 too, when a Company called "Silicon Film" showed a prototype, filed patents, and announced they'd be shipping Real Soon Now. Then reality set in. The product turned out to be a fairly famous case of vaporware.
It's even less of a good idea today, when there's a flood of older dSLR's on the market. The problem is essentially one of a split brain. You either need communication between the back and the camera, or the user has to turn on the sensor when they wish to shoot, adding another step to the process. Similarly, while film cameras were using DX encoding for film speed, that would be a real kludge with a digital sensor, so you'd likely have to set ISO manually. In short, digital backs were a far better fit for the workflow of medium format studio photographers than users of cameras like the EOS-3 or the Nikon F100.
But if you are interested, there's yet another effort called Back35 running on indiegogo and kickstarter right now. They also looked for crowdfunding in 2016, 2017, and 2018. As of this writing they claim they'll be shipping in September. Of this year, even. This one uses a 14 megapixel 1 2/3 sensor ((~ 6.08 x 4.56 mm) which Panasonic no longer lists as current. If I'm reading the claims correctly, it also uses optics internally to reduce the incoming image. For this, they are asking $343. For $100 less, you could buy a camera like a Canon 50D. You'd end up with a far less klutzy package physically, actual integration, and better results.
https://www.indiegogo.com/projects/i-m-back35-have-a-roll-already-i-m-not-jealous#/
But heck, it's your money, your gear, and your choice. Personally, if I want to use FA or F100, I'll use film. If I want to use a digital camera, I'll use a digital camera.