Signing up for a Premium Membership is a donation to help Inside Universal maintain costs and offers an ad-free experience on the forum. Learn more about it here.
The problem is how to incorporate lighting, pyro, & water effects into an existing theatre that already has a show present. Its possible to do, but the amount of effort it would take to make it happen is the reason why we haven't gotten a cool Spectrablast-esque nighttime show. The lack of space backstage to store temporary sets is one issue. We can't exactly have fountains like WoC or UCS due to the watercraft & performers in the water. That's another issue.
With the park currently in heavy transformation, it is difficult to even conceive other nighttime entertainment options due to any location in the park currently being on the chopping block unless it was recently redone.