Where to go, what route, how's the weather, and for how long?

Remember the most important lesson: This is all up for grabs.
So the nutshell seems to be about 4 months, through about 30 countries. That’s that great little big picture sort of view. But how do long do I stay in a place? What should my route be?

One idea that guys and I have kicked around is that I’ll spend about 3-4 in the big cities-the Eurail hubs, so to speak-London, Paris, Helsinki, Rome, all those sorts of travel meccas. But the outlying areas, the villages and small towns, the teeny dots barely visible on the map, shouldn’t be neglected.
Each city can also include some “serendipity time”, to account for the random tips and must-see places you pick up once you’re in a place. And luckily, a place isn’t made worthwhile simply because there are lots of people there. (Sometimes just the opposite is true!)
Here’s some options I’ve been kicking around.

Since I’m traveling during August, September, October and November, I’m going to try to keep up with the warm weather. Northern countries (eg UK, Norway, Sweden, Finland), first, then generally going south to west, and maybe once I hit, say, Portugal, turn around and go east again. Maybe.
Start in the UK. Validate my BritRail pass and spend about 2-3 weeks there (along with some time in Northern Ireland and the ol’ Republic of Eire itself too)

UK & Ireland, 2-3 weeks.

Eurostar, Belgium. Eurail Flexipass Youth validation. (or Harwich UK to Denmark ferry)

Belgium

Luxembourg?

Netherlands

Northern Germany

Denmark

Norway

Ferry: (Hirtshals to Kristiansand, Norway)

Sweden

Finland

Ferry: Hanko, Finland to Warnemunde, Germany

Berlin

Frankfurt

Luxembourg

Paris
And then I broke for more coffee. That’s all I’ve got so far… I’ll be refining as we go…