I think it's a pretty wicked idea, and I hope that some day you do build it. Remember you can always run your own games on occasions. Out here there are people that spend $500 or more dollars on a juggernaut costume and maybe get to use it twice a year.
A few sims here in Edmonton have been future based, a monster gun could be worked into a scenario if you gave a host enough time to give it some thought.
Keep dreaming, and don't lose heart