Possible to Add NEW Diplomacy Options?

Is it possible to add new diplomacy menu options, such as different requests or demands possibly?

A discussion on the main board I started is starting to boil over and i'm about ready to do the modding myself.

I'm looking to make a mod to add a diplomacy option to indicate to the other faction that they have a unit or army (or multiple ones) on your territory, and if they do not want to be attacked, they should leave immediately or be attacked.

Very important also is it to possibly inform the Pope of such, and if he favors you (not intending this to be a pope-o-meter workaround), if you attack, he will not deem you the aggressor since the other person technically invaded your lands without attacking a castle or city.

Alright, thanks everyone. If this is possible, i'm going to learn how and do it!

No, that's hardcoded.