Ripped out the old kitchen countertops and sink in our 1931 home to find an s-trap. The infrastructure appears to be in place for a p-trap (see attached). Any reason why the proposed diagram on the right wouldn't work? Or clue as to why they would have appeared to have gone so far out of their way to install an s-trap?
A lot of plumbing from 1931 has changed for the better.
We know that that the S trap was not a good idea.
We know run 2" pipe to the santee and then a 1.5" trap arm.
The vent can be 1.5" too.
There should be a 2" cleanout on the line too.
If you cap off the previous line, it doesn't matter much where you cap it.