Thinking about it, most of Dom2 troops resemble that of the 1000-1250 era. From
http://www.battle1066.com/:
"Harold quickly assembled his housecarls and fyrd and in a legendary march of nearly 200 miles, covered in five days he made camp about 20 km south west of York around or in Tadcaster. .... He was three hundred miles from Hastings with a depleted if not defeated force. How was he too defend the country now? Whatever went through his mind, he decided by the 2nd October to march south again. In a historic march he arrived in London on the 6th October 1066. Harold stayed in London only until the 11th October 1066 before marching towards Hastings with his men. On the 13th October 1066 he camped on Caldbec Hill, 10 km north of Hastings. Here the most famous English battle would be fought."
York => London ~330km
London => Hastings ~100km
So Harold marched his troops ~750km within three weeks (and they shurely wouldn't have marched any more during the rest of the month). But this is deemed "legendary", and nothing a sane commander would have attempted without the necessity to counter an immediate threat.
mmh, what about a "forced march option" in DOM3, which lets the troops move further per turn, but let them start a battle with 10 points fat.?