Backing up to Basics
The purpose of a ridge reamer is to
Allow the old piston rings
To avoid the ridge obstruction
And let the pistons be removed.

If the rings could be cut opposite the gap
in some easy way
they would collapse
and allow the piston to be removed
despite the ridge.

Anyway to do this simply?

One thought is that if the old piston could be pressed against the bore wall at the gap,
then the opposite side of the old ring could be drilled with a bit whose diameter would be just slightly larger than the old ring.

Oil ring would be toughest to do.

I also wonder what would happen if
the block were hot
and a round chunk of dry ice
was placed on the crown of the piston
to chill it and the rings?