I think I like the idea, but I hope we get more use for archers and foot soldiers, since it still seems to be a lot of waiting, marksmanship as a whole has been in an awkward place for awhile Id like to see some further development of them and maybe some uses for them in siege, such as you need MM characters to man the towers for further range or more damage, maybe even being able to shoot out of them to enemies.
And maybe a counter to that could be your own archers that shoot back with some special siege arrows, unsure, I dont have too many comments about this siege implementation that wouldn't derail into rework archery, I think its a good base and numbers and ideas can easily be adjusted and added to this system