Re-enable package after OTA

Don't think this is possible, but maybe someone here knows something I don't about Android's package manager...

If a device was rooted, and a package was disabled that required root to do so, is there any way to re-enable that package if root is lost?

For example..

Device rooted...
pm disable com.android.exchange
OTA update...root lost... there appears to be no way to re-enable com.android.exchange, without perhaps factory reset, or firmware reflash.

pm enable com.android.exchange now returns 'permission denied'

Any workaround?

Thanks.