Use custom lock screen on encrypted Jelly Bean device

I recently enabled encryption on my Nexus S running Android 4.1.1. I'm aware of all the benefits and drawbacks, and device encryption is definitely something I want. It's currently working fine.

However, one small caveat I overlooked is that encryption requires a password or PIN lock screen. I assumed (somewhat foolishly) that I'd be able to change back to the lock screen of my choice once the encryption process was complete. I like using a pattern lock, because I can set it to not display any visual cues, which makes shoulder-surfing a lot more difficult. It's also quick and easy to enter a relatively complex code.

The password I used to encrypt the device was intentionally long and complex, making it something I certainly don't want to be entering every time I want to check my messages. I don't want to change it to something shorter, because increased security was the whole point of doing this in the first place.

Is there a way I can go back to using a pattern lock screen? I understand that encryption is irreversible, and I don't really want to remove it. I just want my old lock screen back.

EDIT: I notice that changing the code for my lock screen also changes the key used to decrypt the device, which I assume is why you're not allowed to use a different type of lock screen. I very specifically do not want to be using the same code to encrypt the storage as I'm using to unlock the screen. That seems like a terrible idea, and I can't believe it's really the way Android does it.