I noticed all of these screenshots are in third person.
When I spawned the Age of Time mirror1.dif in my server, it worked perfectly, reflecting all bricks and stuff.
Until you went first person. Then you disappeared.
You could always turn on playerStandardArmor.renderfir stperson... and glitch when looking up and down, or when you have a hat on.
Yes, mirrors are possible without engine changes. No, working mirrors are not possible without engine changes.