According to AA, The new FTP900 is the rifle that everyone wants or needs.
In reality, I don't think you could please everyone.
BSA seem to have it about right with dovetail height to barrel.
Tench Regs seem to be the most reliable with very little if any maintenance and very consistant.
Steyer seem to be the barrel that most people would have.
Air Arms seem to have about the best stock adjustments and Ginb make some of the nicest stocks I've seen.
Weight wise though, everyone is going to be different along with length and trigger pull, although I have to admit that the EV2 Mk4 trigger and adjustments is about the best I've ever tried. Never been into buttons, but that's just me. Some people wouldn't be without them so make the trigger interchangeable between blade and button.
Air strippers... again, people are going to have their favourite, so don't bother. Just put a 1/2" unf thread on the and of the barrel and make sure its crowned properly and then fit a thread protector.
There's no reason for a shroud to be fitted for HFT.... in my opinion.... so why bother.
Electronics.... phaaa.... no place in a modern field rifle... but again, just my opinion.
In short, you'll never be able to build one rifle that suits everyone, so why bother in the first place ?