The number one priority with tug and van is get it right first time, especially if your intending to have the combination long term. If you need to change vehicle to tow the van you want then do it. You don't want to be sitting in a caravan park in the future looking with envy at the van parked next to you that you should have bought. You don't want to be changing vans after six months and losing money.
My 2CW.
We have a 20' off-road van 2.8T with independent suspension (a single wheel each side).
You can have any length or weight single axel if it is engineered properly with up to 3.7M rear overhang (12 feet 1 and a half inches).
If the trailer is for transporting a glider it is exempt from the 3.7m rear overhang too.
Single axle glider trailers 10m long are not unusual. I towed this one all over SE Australia for many years. Very stable.
Cheers,
Peter
My 2CW.