Mantis made a very nice looking elevated chainstay design that had an entire rear subframe that was replaceable.
The concept for the design was to eliminate a perceived problem called, “chain suck“
In the early days of Mountain Biking, the use of a third “granny gear” chainring was causing the chain to ride up on the inner ring and jam between the frame and tire, after the chain gummed up with dirt and grime.
It turned out to be a problem that had more to do, with a poorly maintained bicycle, than of the design itself, so the elevated chainstay was a short lived fad, until the advent of the full suspension mountain bike.
Then the design made a dramatic comeback, as this proved to be one of the most efficient ways to pivot the swing arm.