will use of substitution groups increase use range of xsi:type?

	

We were discussing if the use of substitution groups would increase the
range of use of xsi:type, by range of use meaning the range of types
available for an xsi:type to declare itself as.  The source of our confusion
stems from xsi:type being based on the substitutability of types the same as
substitution groups are. Thus the question is if extensive use of
substitution groups in a set of schemas creates a greater number of
substitutable types for xsi:type to draw upon for its nefarious purposes :) 

I suppose at that level it is really a question of schema design and
community experience, does reliance on substitution groups extend the range
of substitutable types.

Anyway we concluded tenuously that there was not a definite reason for it to
increase the number of types.

The question was raised because I was certain I had seen an article
somewhere arguing this point, but I can't find it via google currently.