Phylast, from reading your post, it sounds like you might not be aware of this, forgive me if i am misreading. under game options, on the far right is tactical battle threshold, i believe it defaults to four, and casuses certain battles to autoresolve automaticly denying you the ability to fight them out, based on the number of participants involved i believe. lower it to 0 and it effectively disables it.
The real problem in autoresolve is going to be spells, especially if they start heading the route of say, dominions, a game which acted out each battle, just didn't let you participate beyond a little script of *suggested* actions. can't tell you the number of times some mage at the back of the formation, against orders, raised a fire shield, setting every other commander near him on fire and killing them, when there was zero chance an enemy could get to him. or my favorite, when i had a communion set up with 5 slaves and one master, and i had a nature 1 mage commanding a large army just set to cast vine arrow. for reasons unknown to me, while the communion went off without a hitch, the nature 1 mage cast bezerk instead of vine arrow, for his target, the communion master, who promptly went screaming into battle and died, loosing most of his choice gear and a fat wad of crystals, and screwing up my communion.
If multiplayer is meant to be viable, they are going to have to get auto resolve working to a point where it is useable, reliable. you will get enough twiddling of the thumbs waiting on people with a decent autoresolve, but having to fight out each battle will get ridiculous, and forcing autoresolve on all battles, will get frustrating.
i would prersonally like to see a option screen before the autoresolve begins where you can specify a few parameters. simple things like tell certain units to avoid combat, or set a variable for how much magic you would like used, you know, don't cast, cast freely, last resort, etc. the scripting in dominions, for example, was horribly inadequate as you often ended up forgeting to change your scripts after customizing them for some specific battle, better to have a default and let you quickly customize on a per battle basis.