Sorry for the confusion Chris. To your comment, my thoughts were that Toyota (or any manufacturer) could build an I4 engine that provided better performance (power and efficiency) similar to what Honda has done with their VTEC engines.
Here is a link to Wikipedia on the Ecoboost engines for those interested - http://en.wikipedia.org/wiki/Ford_EcoBoost_engine
One of the great things about innovation is that it generally fuels additional innovation. Competing manufacturers generally need to respond in order to maintain marketshare with the upside being that the consumers generally benefit as a result. I've owned three Ford products in the past: I liked them all and really the only domestic automanufacturer I would consider buying today. But presently, I have Honda and Toyota products in the driveway and enjoy them thoroughly.
Diesel engines in small trucks are used worldwide...just not so much here. I think that small changes in government regulation that would step up to the current level of present legislation would probably facilitate the introduction of the existing diesel technologies. Perhaps a 5 year plan. The diesel engines of today are leaps above where they were less than 10 years ago, so the compromise might make sense.
As for mixing makes...I guess that it always bothered me when hot rodders would take Chevy engines and fit them into Ford chassis. Of course, building up Chevy engines was faster and cheaper, so this helped to fuel some of the retrofitting. But I like keeping things pure myself.