What was there wasn't particularly innovative today or 20 years ago.
The RV system was way ahead of its time and could've easily been repurposed and pressed into service for a Guardians attraction (via square peg meet round hole mentality) if it had to. It would've been very, very easy to make a 45 minute long trip into the cosmos that could've had allowed for enough filmed (screenz!!!) based content that it could've served as almost a new feature film in the Guardians franchise. It could've used the existing system with the moving theater and an animatronic middle and done so with the same hourly capacity as the new coaster; but, it would've done so with two distinct advantages - it would've added "new" demand at the park as guests want to experience new things and most importantly - done it in an attraction that would provide the guest 45 minutes + of entertainment while not being somewhere else in the park. The park could still have added a coaster and had the best of both worlds.
Unfortunately, there is too much addition by subtraction at WDW. This is especially ironic considering their blessing of size. The reason behind this is that the more attractions/experiences that are added - the more that it costs to operate and maintain them.
Imagineers and maybe guests today, associate E-tickets with "kinetic" motion. Coasters, fast simulators that shake and move quickly, etc. Long gone are the days of a leisurely paced immersive experience. Now the thought is wham, bam, upcharge me man and move along to the next experience to put another notch on the belt. This mentality in design is what is causing the bad attributes of SWL's attractions (the need for kinetic experiences) at the cost of high capacity and/or long ride cycle attractions keeping guests out of line somewhere else. This same problem is being faced by the Marvel team as well.
The problem is that there just aren't very many RV systems around that can deliver both kinetic action and long immersive experiences. As I've said many times before that the last great kinetic motion/high capacity/immersive RV system was lost to Universal and Potter with the Kuka robocoaster. The Shanghai Pirates RV system is as close to the mark as Disney has come to that and that is why the battle over how best to put it to use is being fought.
The real sad state of things is if the same "innovation" used in the Guardians Vekoma coaster would've been applied to Energy's moving theater concept - it would've probably worked even better. Easily the Energy RV's could've been re-engineered to incorporate a motion base under their platform and then all sorts of fun could've been had in the projection rooms and stage section... but... c'est la vie.
I'm sure using the existing building as part of the new structure makes much more sense. Just imagine all the building code loopholes they are taking advantage of.