Quote - Well, this is a big problem. Subdivision deforms the mesh, it can work fine on a closed continuous two manifold surface, but if you have a discontinous surface you have the risk to have the mesh broken after the subdivision because two vertices that had originally the same value will deform in a different way.
I have experimented Catmul-Clark and loop subdivision with Victoria 4 and the result looked much worst than the original Vicky even she was all welded.

I generally agree with the first part, but I'm surprised that V4 gave you any trouble when subdividing. Which parts of the mesh did not turn out well?

-- I'm not mad at you, just Westphalian.