A multitplayer campaign would definetly be quite damn good, because aside from having tons of potential and providing lots of extra hours of playability for the game, it can also help cement a good community around the game. And of course, the hilarious potential for good stories to surface from countless battles.
But about the wound system, the tabletop system would definetly be a huge gripe for many because of how it works. The current wound system is definetly not the best, but it works and it's easy to learn how it goes. I'll put an example: Let's take you have a Goliath ganger (base toughness 4) and you shoot it with a buckshot shotgun (shotgunes have different types of ammo). Your chances of inflincting a wound on a target with toughness 4 with a weapon with strength 2 are abysmal. And in a long campaign you can make your gangers tough as hell. Tough enough so they can shrug off las weapon shots like nothing and even bolter rounds.
If there is something i want they did in order to rebalance the wound system is applied to weapons (also because most weapons in Mordheim felt same-y): Ranged weapons have fixed damage but there are weapons that have more damage than others at the cost of certain penalties and such, while weapons with lower damage have certain benefits.
For example, starter pistols would do from 15-20 damage per shot but they have 1 free reload and +10% hit chance, Las pistols would deal 24-25 damage and never fail an ammo roll, and Bolters would deal 46-52 damage and have a considerable penalties to their ammo rolls. I think it's important to make less powerful weapons more practical with several bonuses (like they tried to do in Mordheim with daggers) in opposed to more powerful weapons that have other drawbacks.
This also ties with other things like how armor will be implemented, but that's another completely different subject.