How about considering giving spouse/significant other living in same household given same elite status. Continental did this recently and it was very successful for them?
I appauld Continental's decision and hope that it takes hold. At the moment as you know, Marriott considers the mileage and points to be in the sole possession of the account holder, and not transferrable. I think this is a vestage of the original Marquis/Honored Guest program, where points required were lower, nights fewer and there were no levels such as there are today.