of course we could go even further and ask for "fully customer-configurable cameras" - at least to such a degree we have become used to "customize" cars and PCs ... at the minimum having a choice between a number of different configurations/versions - eg. with/without Video, sensor resolution, Af-system, etc.
Currently foto gear makers product modularity really equals Henry Ford's model-T policy 100 years ago ... "you can have it any color, as long as its black". :-)
Today you can order a small car eg. a BMW Mini with a very powerful engine and most of the very same hi-end features available in large, hi-end, "flagship model" cars ... if you want and are willing to pay for them. But we will not be forced to buy a 7-series BMW just becaus we would like to have a 200hp engine, Xenon headlights and decent A/C in a car.
It's about time photo gear makers (and the consumer electronics guys in general!) get off their high horse an start offering modular cameras with features to be selected by purchasers!
It's simpler installing a more powerful engine, adequate suspension, tires and screwing in some more gadgets in a car than making a 1D IV modular, for instance, also the competition in automotive is much more fierce. If you want something fully customizable get a MF camera and a digiback, you can shoot film or digi or whatever and change prisms with or with out metering. A DSLR is small, and the prices, I'm almost positive, would skyrocket, if you could select stuff like AF and what not.
I'm not saying it's a dumb idea, but I don't think it's particularly easy to do
Anyway, you DO have the option to not get the flagship model.
There is the 7D that sort of does some of what the 1D does. And the most powerful and optional extra upgraded Mini does not come even close to a 7-series
The sensor however, that would be neat, if you could decide on a FF 25MP sensor, FF 16MP, Crop etc etc. But again - production becomes more complicated, prices rise, blah blah blah.