The way I am seeing this is that management, for one reason or another, just wanted some new trains and a paint job no matter what (These sorts of things aren't done as a folly)
But these alone probably wouldn't have gotten a good enough return on investment, so they probably opted to tack on the the extras, then market the package as a whole, all of a sudden it becomes something people might care about. IMO its a perfectly legit stratergy. X2 has already been mentioned, but you could say Moreys did something similar...not as drastic, but they went to the effort of renaming the ride just to get a bit more leverage off the money they spent.
The thing to remember is that coaster trains are very expensive, as would be the thousands of litres of paint needed to repaint the whole structure, but I can guarantee that the extra additions, like music and fire would only represent a
fraction of the cost of the main upgrades.
I think Superman does need some new trains and paint as well, but the special effects and "sound system" thing are going over board and money could have been better spent elsewhere.
But if you didn't put the fire and music on Superman, you'd just be putting it on some other turd of a ride that would still be pretty poor even with the upgrades. For this style of update to really be worth it, it really does need to be a whole package.
Now, with these changes, I think they could really work well if some careful thought was given in putting them together as a cohesive whole.
I mean, on X2 they just put a bunch of 'edgy' things in together (Fire, rock music, black and red paint etc) and this was probably good enough to match the 'flavour' of the ride (I wouldn't call it themed) and the way it was marketed.
But I don't think such a random approach would be as good on a ride based around a Licensed character. Clearly it would be disappointing if they just chose some random famous rock song, and put the fire effects in with no real logic in placement.
I also think that just solely playing the regular superman theme on the ride would be a bit of a cheap effort.
Personally, I'd like it if they thought of some sort of story, which would be communicated to riders in a re themed queue house. I guess the obvious (and stolen) answer is some disaster which superman is involved in saving guests from. The fire and fog effects could then be worked in to represent/be a by-product of this disaster (Rather than just having fire for the sake of fire)
Finally, the onboard audio would be a orchestral piece, composed to match the movements of the ride, while also helping to convey the story
I mean on California Screamin the soundtrack goes through very distinct changes that perfectly match what is going on (The 'setting off' music as you leave the station, frantic music during the high speed parts, anticipation music on the lift hill, 'finale' music as you pull back into the station)
A similar approach would be taken with ROS...eg the parts of the ride with fire effects going off would have very fearsome and perilous type music to convey the feeling of being caught in a disaster,
The famous Superman theme could be used at the moment when superman rescues you,
music at the end of the ride would convey a feeling that you had made it out alive (I guess like the music at the end of IOAs Spiderman)
...it would very much depend on what the story was.