I voted high roof - intially it was against all my instincts as a kayaker used to using a roof rack, but when I came across a high roof van and checked it out I knew my instincts were wrong!
At your height standing might still be a bit of an issue, depending on climate you might get away with only insulating between the roof beams, you will have cold bridges but I reckon carpet lining will help. The main thing is the options it opens up.
My van was converted from a panel van for motorbike racing, the rear 2m has a false ceiling at about 1.3m forming a generous garage area for 2 bikes with checker plate flooring (well...) and plywood storage boxes over the wheel arches. There is a bulkhead in front of the garage, but only to 1.3m. In front of the bulkhead I have a built in sofa, full width (curl up bed or OK for a child - I have napped on it in the daytime) with heater and aux battery and storage under. Above the garage is the bed platform, with a board to pull out over the sofa to extend it a bit. Claustrophobic for some, especially if used with a full depth mattress but I get on fine up there with a thermarest - would easily sleep 2. In front of the sofa opposite the sliding door are some kitchen units (full size house ones) with a sink and hob (the lpg arrangement needs work and is currently disconnected and the setup uses a removeable pump with an external water carrier, which if you rig it up differently could be arranged inside for winter use). Over the cab the high roof area has a big shelf on which sits a TV, microwave and charging panel. It is a very simple DIY layout in the spirit of the professionally outfitted sports motorhomes / bike racing motorhomes and could be improved on in a lot of ways but it gives me a great open living space and somewhere to carry my kite buggy without completely dismantling it - which is great for going away to race weekends.
As for kayaking, I cut a hatch in the bulkhead and when I pull the passenger bench seat out (just 1 bolt for my type) I can fit an 18 foot sea kayak inside the van, my river running boats fit in the garage.
I don't know how big snow machines are, but maybe with a high top (LWB or XLWB) you could build a garage big enough to fit them in and ditch the trailer?
Have a look in the motorhomes section of the forum, there was a recent thread with some links to commercial outfitters who do this kind of thing, one of them I'm sure had photos of at least one snow machine in camper....
Jim