If I remember correctly I tried to do this some time ago. I remember I used funky locomotion and block breakers and block placers.
I think I used a block breaker to autobreak the sap bag. This should drop the sap on the ground too. Then I needed to replace the sap bag on the tree but that created a problem. When the block placer places the sap bag it will not place it against the tree but turned 180 degrees. I solved it by placing the block placer next to the tree and rotated such that when the sap bag gets placed its rotated correctly, but its not placed on the tree but against the block placer. Then I used the moving machine from funky locomotion to push the sap bag onto the tree. I built redstone logic to repeat this process once in a time. I worked. I can try to find the world where I built it and make a screenshot.