OK.... this may be a reason for keeping it, but someone who has a SW might know better.
Once upon a time (long, long ago) I had a '99 Renault Laguna hatchback. We need not go into that purchase
Anyway, as you do, I bought a small dinghy on a well known auction site and had to go pick it up. I was in Aberdeenshire and the dinghy was in Kent.
To do this I had to fit a tow bar to the Laguna and after fitting the towbar it quite suddenly went from being a wobbly blancmange French P.O.S to actually handling really very well indeed.
So the towbar stiffened up the rear end of the car beautifully
Now I'm not familiar with how a towbar fits to a 156 SW but..... and only someone who has done this or knows the 156 in and out can really comment.... fitting one may
stiffen up the rear end of the car considerably. Which might
be a good thing, on the Laguna it transformed the car. On the 156 it might.