Not speaking for Dan, PJ, or anyone else higher on the totem poll here, but I think I can answer this one. It's not going to happen, for a variety of reasons.
First of all, it would be a rather complicated and expensive kit. That's not necessarily enough to eliminate it from consideration, but the market would be rather limited as high quality FM broadcast stations are fading at a steady rate. Those that still exist are shifting their broadcasting to digital. Remember when TV switched to digital signal only? That's just around the corner for radio and for very similar reasons (namely, it doesn't matter that its bad for consumers, it's good for corporations). Personally speaking, I was considering investing in a high quality tube unit when I lived in Boston and had numerous stations I enjoyed (WMBR, WHRB, WZBC, WGBH has its moments, WERS if I was desperate, WJIB in the car with the wife). Since moving to the west coast, my old KLH is more than enough to pull in the stations I can when I feel capable of tolerating the terrible decisions program directors make here.
Second: building a tuner requires the ability to align a tuner, which involves equipment most people don't have access to and even the people that do don't necessarily know how to use it. That's a huge burden for tech support right there.
Third: Does the name mean you were thinking AM/FM? Double the circuitry so I can hear that I'm going to hell in high fidelity...
The bottom line is there are a lot of great tuners out there if you've got good signals to listen to. If you need a project, find one that need a recap, then send it off to get aligned and enjoy. Also remember the oldest rule of tuners: a lesser tuner with a great antenna sounds better than a great tuner with a crappy antenna.
