Yeah, shouldn't be able to attack twice. I do like the idea of an ability to kind of attack while dual-wielding shields, though, and hope it gets kept. Just make it a "strange weapon" type... which I think should get its own weapon class, which would hold anything you can attack with, but which isn't a traditional weapon. So, Large Rations, potions, things like that, all of them would be "strange weapons". And while they wouldn't give anywhere near the bonuses that normal weapons would, it would at least give you a bit of an advantage.
In short, shields should be like any other non-weapon when used as a weapon - given a rather lacklustre attack strength, but still functional in the right circumstances.
Hrm, I don't know if it'd be necessary to add a "strange weapon" category (you mean for actual weapon skills, right?).. I just don't think it would be worth the trouble really.
I do however like the idea of bashing things with shields. Whether it's implemented as a class power, or special attack of some sort, or even just something that anyone wielding a shield can attempt (who knows the grand complexity of the future combat system? Probably not even TB at this stage).
Depending on how it's implemented (if at all), any turn spent attacking with a shield should probably have some sort of penalty to your defenses (logically, anyway).