The toughest obstacle in being an Arms OT is that the Arms style is heavily reliant on +Crit, and that Tanking gear does not prioritize Crit in any way. Because of this, you probably won't be dealing that much damage if you're in your tanking gear even if you switch out your weapons. However, you'd still be a formidable tank in tanking gear, and dish out DPS in your DPS gear, but you probably can't do either job well in the wrong gear.
If you have a chance, read over The PVE Arms Warrior Compendium & FAQ 1.0 located on the wow forums since it goes into good detail about the pros and cons of being Arms and the tanking utility involved.
I know you mentioned that you're not interested in Fury, but coincidentally, a lot of tanking gear has a lot of desirable fury stats, such as Hit, Expertise, and Strength. Couple that with the fact that when you equip two 2-handed weapons (which you can do in combat), you get a huge stat increase, so theoretically, you could have an easier job of DPSing in your tanking gear if you needed to, or if you're placed in that situation more often.
But anyways, I hope this points you in the right direction!
Stay strong. Stay smart. All heart.