Good day Antoniogm!
Have the conversation with a good rigger but I expect they will say stick with the wire diameters that you have. When the boat was designed, all the standing rigging would have been spec'd for the boat's needs including a safety factor. I assume you are not adding huge new sails so the rigging loads will not have changed. Ironically, I would expect that the quality of the wire will have improved over the years and the loads supported by the 7/32 wire are now slightly higher than they were previously.
I believe the lower shrouds on my boat are 3/16 wire but I would have to check to be certain. I would expect these to be lighter than the upper shrouds.
In terms of the backstay configuration, our set-up works like a charm and I see no reason to change it.
On my boat I have 1/4 wire for the forestay which I had to replace four years ago as part of a repair to the furler. At that time my rigger said that the 1/4" wire was overkill but I stuck with it for peace-of-mind as the wire lives hidden under the furler extrusion.
Also, ask the rigger if your standing rigging *needs* to be changed. In my experience we sometimes get projects into our heads that are not necessary or can be deferred in favour of other projects.
The pedigree of your Contessa ensures that you won't sound like an ignoramus because you've chosen such a great boat!