Hi, were planning roughly the same, but some 1 - 1,5 months later. Were riding 2-up on a Vstrom 650. Some areas seem interesting to say the least, if you look at the news about Turkey, Iran and Pakistan right now!! I hope it´ll be more settled later on this year...
Hope you will update your blog as you travel, as it would be truly excellent to get some fresh info about things. And if your schedule is so flexible as it seems, who knows maybe we can meet you somewhere along the way!
About carnet, as I understand youre going to need one.. are you getting it from your local automobile association, and how big is the "guarantee"/deposit that they ask from you? See, here in Finland they want 5000 euros to issue it for us!! I hear it might be possible to get it with a smaller deposit from Germany, Im working to find that out.
Do you have any insurance on your bike (against theft&fire) that´ll be valid outside Europe, or you just trust your good luck? Im finding it hard to get any company to even offer one and the bike´s almost brand new (bikes cost a fortune here because of our high taxes). Thats something I´ll have to get a solution into.
What tyres do you plan to use? And will you carry an extra set with you (Im hoping to avoid that, but not sure at the moment if I still better do that)?
As far as Ive been informed (never done this route myself, though) your plan seems realistic, except maybe for Vietnam where your probably not allowed to go with a big bike.