As for the sensors, in the "Major brands" Canon makes their own as does Panasonic, almost all the rest except Olympus, use Sony sensors.
Lets see, Kodak sensors are still in use, Leica use a Kodak sensor and pretty sure some medium format cameras are Kodak sensors.
Now we have Leaf, Mamiya, Pentax and Phase one all making medium format (and Leica if you include there S2?)
I dont think Kodak make all those sensors and not aware of any sony sensors that are medium format, Kodak and Dalsa are used. http://en.wikipedia.org/wiki/Image_sensor_format#Medium-format_DSLR
Also samsung make there sensors, being a large electronics company like Panasonic, it would be silly to outsource this item. This saw a range of similar DSLRs from Samsung and Pentax, just like Panasonic, Olympus and Leica with the E-330, DMC-L1 and the Leica 43rds.
Also Nikon uses sony, at least for the APS-C sensor cameras. the D200 and D300/s are both sony sensors.
Pentax K-7 is a samsung sensor.
So not even close to almost all the rest except olympus... take out canon, you have sony, olympus, panasonic, pentax, samsung, sigma, nikon and fuji.
fuji, samsung, panasonic, sigma and sony make sensors.
pentax use samsung and sony, while olympus use panasonic.
nikon use a mix of sony and bespoke sensors.
if you can imagine the picture, then do all you can to make it