I fiddled a bit with a script in which generals would get movement points as long as they stayed on friendly ground. It would help to ease the boring task of transporting reinforcements in the end game when your empire is huge and it wouldn't be too unrealistic since armies have better supplies in their homelands. But the trigger does not seem to work well as it goes off in both friendly and enemy lands.

Sadly enough CA doesn't seem to realise how much modders can achieve with scripting and doesn't want to invest any time it.