Thank you!
In theory, the mechanic is somewhat simple (storing player positions/rotations every time step in a big list and playing them back at the same speed). I foolishly thought that would be the end of it, but once I got physics involved, it became an absolute nightmare, since physics in Unity isn't entirely deterministic. Meaning sometimes there could be random alterations in how the clone pushed something (from minor frame drops or floating point errors and whatnot) which could lead to it destroying artifacts, etc. That was definitely an unforeseen challenge.