Re: Lifesize ED-209 Build. Check it out. You have twenty seconds to comply...
I wasn't necessarily a 'little kid' when i saw RoboCop but of course i loved the ED-209. Didn't get enough screen time IMHO. Like everyone else on this forum i am totally blown away by your sculpting skills.
I design things on the fly, usually roughing in the basic design in the first 10 minutes, in my head. I not so humbly believe i'm quite good at it. For instance, last night (2am) i was pacing back and forth on the deserted highway out front designing the cocking/ firing/ safety mechanism for the anti-personel rails on my 1:1 scale improved M583 Aliens APC build. Currently in design stage. Also the vertical-launch guided missles, the grenade/ flare launchers, the telescoping antenna mast, the RPV drone tubes, etc. Every time i daydream about it i rework various systems. Yes i know i sound crazy...

I see amazing robots/ guns/ vehicles on the movie screen then my mind goes to work trying to figure out how to build it and make it work for real.
With a tiny bit of rework courtesy of your father ED could be made to lift one leg and turn (pivoting on a trailer spindle in the other foot). If you wanted to keep it cheap you could build linear actuators from salvage-yard windshield-wiper motors or motor/ planetary gear drive from cordless drills turning allthread. It can easily be made to track passerby with this...
Real-Life Sentry Guns for Sale - Software Starter Kit
Software (running on a WinXP platform with decent graphics accelerator) analyzes video from a wide-angle fixed camera, identifies and tracks targets using a servo-controller moving x-y servos, with a Z solenoid/ servo for weapon firing if so desired. Software is FAST and will accurately predictively LEAD the target. You could also put a 60" monitor behind/ beside ED displaying the tracking software as it paints outlines around potential targets (people) walking past in the lobby. Just some food for thought.
If you put a 2.1 logitech computer speaker system inside ED the Bose-style Accoustimass sub would add authentic servo/ diaphram-rumbling sound to ED. Or build a Wicked One subwoofer cabinet and drive it with a 500 watt off the shelf amp. For audio reference
https://www.youtube.com/watch?v=ldsYjFRsRU8 You could jump to 1:50 to avoid some BS.
You might also benefit from software from this site...
Lynxmotion - Products