The Viper had a strange life, being designed to be 'used once & throw away' and built to an appropiate budget, and then been used as a proper engine.
Did anything else in aviation compare?
It was originally created as a drone engine, but when DH designed the 125 it was available, and cheap. I don't know just what modifications were incorporated to make it a 'reusable' powerplant, but there must have been some. My Government friend used to say the joke among FBO employees was "Check the fuel and fill up the oil." I seem to remember there was a
minimum oil burn specified in the operating manual, of one pint per hour. There was a little mini pump that sprayed oil onto the number five engine bearing and if the oil consumption was less than a pint it meant the pump wasn't doing its job.
There was a company in the US, Culver Aircraft, that built a drone that later became a two-seat puddle jumper they named the Culver Cadet, so that's about the only thing that comes to mind that is remotely similar.
Culver Cadet