-
you can't go into Serbia from it.
My route goes straight into Mac from Kosovo so perhaps not the issue I'm imagining it to be? I'm sure I heard of fighting or something near borders though.
Flat but coastal winds?
I have high and low routes across the alps - Italy isn't flat up there though is it so I have no idea which way to go. This whole thing is a rough guess, never having cycled any of it.
My main thing is just avoiding stuff that will require on the fly rerouting. I don't care how long my route is I just don't want to get to an illegal tunnel or something and then have the stress of working out how to continue.
The main issue with Kosovo is that you can't go into Serbia from it. I think the other borders are ok.
When I did a route in December, I did something pretty similar to your Greece version - it was shorter and flatter than Bulgaria.
For 3 to 4 mine was mostly a mainish road quite close to the coast, then a little bit of Bosnia. It seemed flattest.
For 2 to 3 I was mainly planning on staying in Switzerland and taking my punishment in the Alps, but going by some Facebook chatter, some people are planning to cut South into Italy a bit sooner and doing something slightly longer but flatter - I'll have to re-visit that bit.