Had a slow leak; bottom of cabinet sagged a bit. What to do?

I guess when I was replacing my RO filters last time I did not tighten one of them quite enough, so I had a very slow leak under the sink. The leak was slow enough that it caused the bottom of the cabinet to 'sag in' a bit under the 5 Gal water tank (green ellipsis in the picture). There was about a cup of water in the lowest area. To give you an idea, the leak was so slow that we never noticed any water coming out of the element nor at the bottom, under the element. It's all dry. I cleaned it all up now and have a fan drying it but - I am thinking to cut out the sunken part, so I can dry and clean up everything that's under also. I plan to make cuts like the red lines show. Question: is there an obvious flaw with my plan? There is a granite countertop above, but I do not expect that a cut like this should cause a lot of structural problem? Image: https://ipwkva.bn1302.livefilestore.com/y2pHQGOmKq0FoEhND3UyRg5AU3UKjPK8dMkhvknzq6M9yvo4L6I5T_DLNoroMFTHx6dmwcjlvVOn7mX4NnMjIOn7wfUj7nV_NtL6FGO6ARAXM0/sag.png