If Paul were here he'd probably wonder what all the fuss was about. But with regard to how Paul would handle this situation for another, we can only guess. Based on what little I knew of Paul, which seems to be clarified by many posts here, he wasn't one to promote his good deeds. When he helped, he usually helped as anonymously as possible. If someone started a thread on the Wall about a problem they had, and he had advice to offer, he usually wouldn't post the advice to the thread, he'd send a PM. He likely took the same approach to charitable donations, as it seemed to fit the code he lived by. He would likely not want to put his name, personally, or in aggregate, on something that was donated. So not only do I share the "fuddy duddy" view with Ken and Jack, that putting even an abbreviated logo feels too "look at me," but I feel that Paul would feel the same way.
But, as Ken already said, those of us who object can simply find other ways to honor him. Since most are either ambivalent or feel that it's "our stone/BiB, it should have our name," that's cool, go ahead. Paul might get some amusement from the people who look at the brick and say: "What does this mean: 'In memory of Paul and Darlene...To Be Determined'?" What's important to me is that people seem to want to do something good on his behalf, and I would heartily encourage those who feel that way to find a way to do it, through the "TBD" paver or another means.