I believe there is an additional business opportunity here that you might consider (or perhaps you have, and may have discounted it for reasons I haven't even thought of).
If you were to re-phrase that sentence to include:
"
Unless other arrangements are made in advance of the session, the creator of the
image(s), the photographer retains full copyright to any and all images created by the
photographer. The clients desire to purchase the copyright to the sessions images must be stated,
and compensation agreed upon, prior to the initiation of the session."
You have the right to sell your copyright to the images. If your client feels uncomfortable with you
retaining that right, or simply wants full control over the images, then you can certainly apply an
appropriate financial value to it, and receive just compensation for assigning it to your client. I might
also add a legal caveat to that part, stating that the images shall not be modified in anyway once
presented to the client.
This would also be another option on your list of available services, as some clients may be fearful
of allowing another to have copyright over their photo's, and as a result they would "opt out" of even having them taken. Granted, you risk giving up the right to a "million dollar" image, but that is also the very risk they are compensating you for, and prior to your ever pushing the shutter.
Always been a firm believer that, providing it is neither illegal, immoral or unethical to do so (and I
too have high standards), then
anything is negotiable.
Mike