I got the idea that might interest you to develope a kind of new half kit...
How about a tube module kit that consist one 9pin tube and basic component around it ie. grid resistor, cathode resistor and bypass cap, plate load resistor, coupling cap and load resistor.
It has the flexibility by changing those component values :
- single stage pre or 2 of them can be phono pre with RIAA insert between them.
- configure as cathode follower for buffer or upgrade a CD player output stage..
- Connect the two triode in some kind (B+ jumpered to cathode of another triode) of SRPP stage
- even as a driver and splitter stage for PP amp..
- the tube selection flexibility 12A..7 family 6DJ8 (with different filament config)..
It might be interesting for experimenter and upgrade, or as an entry point to DIY tube world
You could use your experties in developing good PCB, and maybe also develope a power supply board for it...
Just my idea... i think it would sell very good like Buggle aa