Importing and editing vector images

[buggy]

A client of mine would prefer that I provide them with vector diagrams in
Visio format, so I am evaluating the product for purchase.
I typically create the drawings in 3D and render them to a vector format
such as AI or Flash for further editing. I see that unlike the other 2D
vector drawing tools that I use, Visio is very limited in what it can import
(only SVG).

That said, I am able to import SVG files into Visio, but the way it
automatically groups the lines of a 3D image is very strange. I would like to
be able to break the groups of lines apart, re-attach the lines to those that
will share common line styles and apply different line styles to each of the
new groups. However, there doesn't appear to be a way to break apart the
images (I tried the ungroup option but it is unavailable beyond the first
level). I can't even remove a line segment -- the freeform drawing tool will
let me delete a point but then the line is automatically reconnected between
the remaining points.

How do I edit these SVG images in Visio? Any input would be much
appreciated. I have to decide what to do on short notice.

Thank you.