1) Van vs mod in winter weather. Drove mods in blizzard conditions no roads plowed, no chains, did not get stuck once. Vans stranded all over the place.
No vehicle is infallible. Look on Youtube if you think Type I, III, or IV (medium duty) ambulances always do just fine in winter.
2) Critical care transports, RN on board, pumps, equipment. No room for anything.
Type IIs would be cramped, that's true. But CCT is one specific purpose. You're question is should Type IIs be banned, period. For BLS stable-patient IFT transports, for one example, Type IIs are fine.
3) High winds: I've got blown into other lanes on a two lane highway with out turning the wheel.
If you got blown into another lane without turning your steering wheel, then YOU ARE DOING IT WRONG. If you're getting blown into another lane while holding the wheel straight, then TURN THE WHEEL. It's really not that complicated. There is no demigod of EMS that's going to get angry at you because you had to turn the wheel to go straight. If you get blown into a car in the other lane, what are you going to tell them—"Sorry, but I was holding the wheel straight?"
4) Reaching over a pt if you need supplies when transporting.
In all the Type II units I've been in, the stretcher is oriented longitudinally on the floor, with cabinets on the left wall. In all the other kinds of ambulances I've ever been in, the stretcher is oriented longitudinally on the floor, with cabinets on the left wall. Oh, there are a few cabinets above the bench and behind the passenger seat, too, but the stuff that gets regularly used is almost all in a cabinet on the left wall. In my experience, in ANY kind of ambulance I've ever been in. So it seems to me that I'd be reaching over the patient in ANY kind of ambulance.
5) Limited space for equipment.
Isn't this just a repeat of #2? No ambulance has infinite space, therefore every ambulance has limited space. Some have more, some have less. If you work for a service that has so much stuff they need more space than a Type II can offer, then your service should buy bigger ambulances. Seems like a pretty simple solution to me.
I don't see why Type IIs should be banned for everyone just because they're not perfect for all situations.