larger gas tank

i saw your new 2014 transit xlt passager van that has a 2.0 l 4 engine and it has a 15.4 gal tank on it and it can go 350 miles on a tank gas. why not put a larger tank on it so it can go 3 states like a 25 to 30 gal gas tank. i would love that becuase it will save me money in traveling and will not have to buy gas for two months. and it will save going to gas stations and cut back on our fuel problems too.

thank you
randy gravitt