This question has in fact been covered on the FMTuners group, and the general conclusion has been that unless you're insane, doing one from scratch would be a fool's errand. This isn't a preamp, like you wisely noted.
Building a modern high end tuner would require more than I care to think about. Even the "tuner companies" like Magnum and Farfare haven't bothered to do it, really. They still rely on a lot of car radio parts and VERY dated designs with dual gate MOSFET front ends!
To do it from scratch, you'd have to be a filter expert to do it right to design and build relatively sophisticated group delay compensated 10.7MHz filters. Then you've got to design yourself a PLL or ratio detector. Then you've got to design an LA3450-based setup for the multiplex, or a discreet analog multiplier setup, not to mention an interface.
This is why most people just prefer to modify existing tuners, and don't write books about building your own. If you pick the right platform, most of the work will have been done for you, and you'll have some decent shoulders to stand on. My current cheap tuner to mod / redo pick is a Yamaha T-85 or TX-1000: Already have the jFET RF amp (not perfect, but better than MOSFET!), balanced mixer, a group delay EQ'd IF, very quiet FM detector, and an analog multiplier stereo decoder. You can put better IF filters in, replace the opamps used for the stereo decoder, replace capacitors, resistors and what not, build a new / addition power supplies, you get the idea. Basically, play with parts. Not a piece of "by the book" car radio chips in sight. I have yet to find a comprehensive "do it all" book.
Regards,
