How can I re-route a venerable wisteria?
 

We have an old (40-50 years, I think) and extremely vigorous wisteria on
the south wall of the house - its trunk is probably some 10 cm in
diameter. Unfortunately, it is bent, and very close to where we are
going to have to have replacement windows installed sometime very soon.
However, there are lots of shoots coming out of the roots, and I have
tied some 8 of the best-placed ones to a cane with the idea that these
can take over when the main trunk has to be cut.

My hope is to have the replacement wisteria flower as soon as possible.
Presumably, with the huge root that this must have, this would be much
quicker than replacing the wisteria entirely? - If that is the case,
then we would much rather leave it, even though probably there are much
prettier cultivars these days, with longer trusses.

My question is: is it better to have more stems, in order to have a
thick, twisted trunk - or would just a few grow better than 8?

Also, the shoots are very long already. Should they be cut at the point
where we would like them to end (it regularly attacks the gutters in any
case, and sometimes I wonder if it plans to strangle my daughter in her
bed), with the aim of getting side-shoots in time, or should they simply
be tied in horizontally from that point on?

Thanks in advance for any advice!

--
Klara, Gatwick basin