While a shield using warrior might be fun, I think it would be best just to come up with a completely different weapon type to go along with the shield and then combine attacks using said weapon and shield. Giving a blademaster with one sword double damage and 1.5x wounding wouldn't be good enough to make them viable. As an example, pinleg is a blademaster's main means of keeping someone from running away. If you only have one sword and pin, well, you can't really do much else unless there's some sort of synergy with the shield. One hander afflictions at the same wounding level are also typically easier to deal with and cure than the afflictions given out by two handers at the same wounding level. This would need to be accounted for in some way.

And unless it gets tweaked any time soon, I doubt you'll find too many forgers that would be eager to take up more "business" than they already have.