Rather than hinge to floor, put a pivot in a little ways from end and a lot of
counterweight on the short end that rotates off
stage and up. Possible to balance it so one person can easily raise or lower it. Think about 1/4 ply on both sides of 1 1/2" Styrofoam (don't get me into fire code issues), pivot centered in 4' width and in as far as possible - but even if just 2' from end, and maybe the down/off
stage end is a half round, just more wait but should be easy with foam and ply. Maybe thicker so it can be climbed on. Or if you want it higher - put pivot higher and (which gives more back end for
counterweight) and fill in below. Maybe a
flipper panel off main piece or maybe even a cloth
drop. You need a good pivot but not friction less by any means. I'd think about pipe and speed
rail. A couple of sheets of 3/4 ply on end that sandwich the
barricade, well anchored, might be fixed
base of pivot. And no heavy framing in onstage end - maybe the 1/4 ply and just a one by perimeter framing - carefully made and glued. Think about cement blocks (the solid kind - not cores) or clean pea gravel for
counterweight. (Or for a twist on hydraulics - water tanks that you empty and fill to control it! - forget that, we;ll have a pit drowning next.) Better too much weight because easy to add on long end. If you wanted to jazz it up, use a linear actuator to drive it - much cheaper and easier than hydraulics. This will take some calculation but that's the fun part. Make sure the weight is well contained and anchored.
You know - if 6' or so high is what you want - just make the part more than 6' above the floor that wide - because floor space shouldn't matter above head height so much.
Balance is supreme in all things rigging and scenery. Much better than out of balance and brute force.
You might want these to lock or mesh at center, and you might want a
jack on back if actors are rough.
Need more compact? do same but shorter pieces and telescope from tilting piece when it's down - so
gate closes and an actor grabs a handle on back and pulls it onstage till they meet. Like a plywood box that sleeves over the pivoting part.