There is the SR MTE-100, an adjustable setback MTB post (with quick release so you can easily adjust the seat position). Goes from about 20 - 80 mm setback. I have one set at 65. Most I have seen are 26.6 diameter which shimmed out nicely for me to 27.2 using garden sheet aluminum from Home Depot. These are long out of production but google them. They are still to be had.

The forward rotated position you talk of is something I do - on my fix gears where I may be riding long distances upwind and don't have the option of gearing down. Definitely NOT what I would choose for touring. There is a lot more weight and pressure on my hands and this is with changes probably half the 2 cm you are talking.

My take on seat position is that it is the most "sacred" measurement on a bike. I won't blink at spending real money to get it right if that bike is going to get any serious use. 2 of my bikes sport custom posts. A third was in line until I stumbled on the MTE-100 (for $15!). "(T)ouring bike, with some training and cyclocross" sounds serious to me.

Ben