It seems to me that there are two arguments developing here from standard split. To begin with, that it is wrong to modify an early volkswagen by fitting seatbelts because they are collectors items and shouldn't be modified. And now that there's no point fitting them because early volkswagens are not safe to drive around in anyway. Obviously this is a discussion, and in a discussion points develop, but this is a bit of a leap. Is there a definitive reason why seatbelts shouldn't be fitted, or is it a bit of both?
Personally I believe, however beautiful, rare and collectable vintage cars are, they are cars, and cars are to driven, otherwise I'm not sure what the point is in them still existing, and thus if you have children you wish to carry there is no choice. Secondly, I think the 4x4 argument is a little bit irrelevant. When these vintage cars were modern there were plenty of large and much less safe vehicles on the road to have collisions with, and moreover, horrific accients, whatever car you or van you are in, lead to horrific injuries.