Adam, I think you might be missing one important detail (or at least your post did not mention this detail). The prohibition against foreign systems above panels is for the first six feet above the top of the panel. If the panel is installed already and someone runs a pipe above, and less than six feet above, the panel, then something must move. You can't resolve that by simply adding a drip pan to protect the panel. The first six feet above the top belongs to the electrical installation. Put a pipe seven feet above the top of the panel and then install a drip pan, and you will be in compliance with code. Move the pipe so that it is no longer directly above the panel, but is instead above the working space, it will be OK, as long as it is at least 6'6" above the floor. That could be the easiest way to resolve a conflict.
Please note that the "dedicated equipment space" rule only applies to four things: switchgear, switchboards, panelboards, and motor control centers. These are the only items that once installed could undergo a future modification to add more conduits. I believe this is the reason for the rule. It is not just about protecting the panel from drips, it is about leaving room for installation of future circuits.