It's "Elo" (not an acronym). There is the Computer Chess Rating List (https://computerchess.org.uk/ccrl/4040/rating_list_all.html) which has the current rating, on some predefined hardware.

The easiest way to do what you're discussing is just giving less evaluation time to the engine - slowly increasing it. If you wanted it to be even better you could calibrate multiple engines to make an even smoother (but changing underlying evaluation).