markyboy, a longer ranger 321 would be a really useful thing to have- I've sat in a number of Middle East airfields looking at the OFP and the forecast headwind and wishing we could put on another tonne of fuel.
Unfortunately there are two problems. The less serious one is the size of the fuselage- you can fit in some extra tankage (several of ours will hold 21T, a bit more if the fuel is cold enough) but eventually the extra tanks start to cost hold space.
With some revised loading procedures, you might fit some fuel into the tail, but that would still come up against the more serious problem- the wing just isn't big enough. At 79 tonnes we are really struggling to get above FL330- any more weight and the cruise starts to get into turboprop country. What some of our routes really need is a 322- a 321 body with about 10% more wing. I don't see that coming into production anytime soon.
Anyway, this is really thread creep- like most of the posters here I have always loved the 757, although it seems unlikely I will ever fly one. I hope to see them around for many years to come.