About diplomacy:
The suggested "Get off my land" option mentioned several times sounds great to me. They should REALLY add this. Should've done it as a standard option long ago anyway.

But I have more about this thing. There's this option where you can 'declare a cancellation of Trade Rights' or to 'declare a cancellation of an Alliance'. But it'd be good to see them used in more ways. For instance if you can THREATEN to break an alliance or to cancel trade rights.
What if a faction is your ally and supposedly depending on your military power to assist them? You want something, they want something: demand something and threaten to break the alliance and with that your military assistance.

Same thing for economically weak factions or factions depending on trade (as they all do of course): if there is much trade between yours and theirs true your ports and/or roads you can threaten to cancel the trade.

Example:
You and a faction are neutral and engaging in trade rights, but you're planning to conquer them sooner or later. But to avoid war for some time you'll prepare to weaken them by canceling your trade rights. You do this because maybe you have enough trading connections established anyway or whatever, making lots of money each turn, and you could deal well with it as they'd actually lose a big chunk of their income. Just imagine the possibilities.
Even more! What about pressuring OTHER factions to cancel trade rights with your neutral but soon-to-be foes? When I think of it...... oooooo
Of course when you would force or convince other factions to cancel trade rights or even alliances with them, your relations might worsen with one and improve with the other. Also the reputation should be handled carefully.

Many possibilities