That's why the maker uses fabric tape instead. Longer lasting and doesn't gum things up as bad as deteriorated vinyl tape.
All old cars develop the 'bad trunk harness wiring' sindrome. No escape. In my old Fords, I've had lasting success by wrapping the harness in rubber self-amalgamating tape. After a day or two, it fuses into a seamless rubber 'tube' that closely encases and protects the wires. The UK-made MotorMite brand I find at AutoZone is reasonably thin and doesn't increase harness diameter too much. Don't know if a harness wrapped like that could be teased thru the trunk access holes and rubber hose in the Bimmers.