LH2, my experience of getting CAS transits was more sporadic than you suggest.
Belgium was easy, Germany is easy enough anyway, Swizerland would not let me into its Class C (even though I was ~ 1500ft above the peaks in places), in Italy one ATCO would clear me A-B-C-D (all in CAS) and at B hand me over to another ATCO who ordered me to remain OCAS
resulting in an instant dogleg out of CAS and me spending the rest of the Italian transit way out over the sea, near Croatia. Croatia is very easy and a piece of cake to fly in.
It would be a bold pilot who just plans a route across Europe right through CAS. It might work... but all you need is one ATCO who got off the wrong side of the bed that morning, and you need a 2nd pair of trousers (and a good GPS).
I haven't yet been further east (say Bulgaria) will will be doing Istanbul (via one fuel stop in Slovakia) this year. Regrettably this will all be IFR.