I bought a bike with bigger wheels for a faster ride. It is the Airnimal Joey. I still have my Brompton, but it's now only a bike to do shopping with. The ride of the Airnimal Joey was that much more enjoyable that I only use my Brompton if I really have to.
So I'm curious if you have the same experience after you have bought a new bike.
I did try to do mountain biking on a Brompton. My advise "forget it". It's simply not the right bike for it.
Just as racing, the Brompton is simply not the right bike for it. But for city touring, short trips, maybe even longer trips, the Brompton is made for.
And of course folding, that's what the Brompton surely is made for.
But for mountain biking the best is to go for a bike made for it. Although very expensive the Airnimal MTB is a good bike. I did ride it once and I really like it. But for now I stay with the Airnimal Joey, not for mountian biking of course.
So there is a bike for every purpose.
Of course everyone may differ in opinion. That's what make this world so special.
BTW that Thorn Nomad S & S looks great! But I don't have the guts to ask for the price . . .