Currently when doing a blend on two bezier curves, OO usues polygonial
approximations to create all the intermediate curves.
I understand that it is non-trivial to create a good blending algorithm where
the intermediate curves are bezier curves too.
However this is only the case if the two original curves have different numbers
of knots. If the have the same number of knots, how to produce intermediate
bezier curves is quite obvious, isn't it? Now the spezial case is also the case
which is most important for power users of the draw module, because they,
wanting to have maximum control about how the blend is performed, will where
possible use this special case.
So if you could provide a bezier-blend for this special case, it should be
a) considerably easy to implement
b) very useful for the audience considered: the power users
(which implies, you'll have them of your neck bugging you with requests for a
full functional bezier blend  ;-)  )