My recommendation would be to run your own DNS on your own IP addresses. Even with the IP shortage, you should be able to get a small block delegated to you that you can use for your mission critical apps. Once you've got that arranged for, its a fairly trivial task to find a registrar with policies more complimentary to your business.

If its mission critical for your business, then you can't afford to think like a victim. Take charge of your infrastructure where you have to. Relying on third parties is lean, but not always effective - a small amount of fat in the right areas can give you a lot of flexibility (and insurance) that you might not get when you rely on a third party.