First, an answer. If you try to modify the Arione, it very much does matter which model you have. If the base of the saddle is composite, then you could make a cut out. But it is unlikely to last very long. I expect that the filler materials, the gel, the foams will simply move out of place out of your new cutout.
If it uses the woven base, the one that is soft material like kevlar, then you won't be able to make the cutout without damaging it at all, IMHO.
You are complaining about a product which you think should be designed better, but the fact is, it's a product which works for a lot of people as is. There are a ton of other saddles with cutouts that you could choose. If you don't own the Arione, you aren't locked in to using it, as you implied in your question. So find a saddle that works for you, rather than buying a saddle you aren't happy with, and trying to modify it. It makes no sense.