IMO the ending fix is needed far more than some additional black lights. I just rode it last weekend and don't think I once noticed any distracting supports, rods, wires, etc. in the under the sea sequence. I wasn't looking for them, sure, but then again, 99% of the people who ride aren't looking for stuff like that. Fact is, if you're looking for things like that, you can find those types of things in most attractions.
The bigger distraction is the ending. Jumping straight from kiss the girls to Happy Ending with a tiny reference to Ursula's demise in the background? I've had an issue with that from the start. Why gloss over the climax of the movie? Maybe they were trying to not be too scary, or budget cuts, or whatever, but feels abrupt, awkward and strange to just end it like that.