As an additional note, if you build siege towers; which clearly indicates you plan to go over the walls, not through them; the guns still focus on destroying the walls rather than the guns that are killing them.
Regarding your suggestions, I agree a court system/messenger system would be a big improvement. Other clans get mercenaries easily, but once you become leader, you don't have the time to contact mercenary leaders. They should have a contact in your court or you should be able to message them. Also, quite frankly, when I am regularly leading armies for the never-ending wars, I don't have time to track down other lords to ask them to join me. There should be a system where either I should be able to message them or, when a small, dying empire has less territories than lords, they should be able to contact you at your court for them to propose joining your empire.