Flachy,
I'd definitely go Long Wheel Base (lwb). Can't see any reason why you wouldn't. You can have a seat in the back and you still have heaps of room behind it to load gear and sleep if necessary.
The back seat adds a lot of options. - transport more people, can use it as a separate area if you're camping out, keep your wind surf tub in there, etc.
On the Hi ace thing. - my mate has a 94 Hiace lwb. Uses it for surfing, Wsfg. He reckons it's great. -solid as. You know mines an Econovan lwb. I'm wrapped with mine, but I would've prefered a hiace if the right one had come up when I was looking. (bit more solid and better resail value)
My first van was an '82 Hiace.
Got it in '89, finally died in '98 (R.I.P "Gus the Bus"

- Rusted out)
Fowles Motor auctions are a good place to get a good deal, but you need to do ypur homework first.