You are able to rout the slot to make it wider, but you'll need a dremel-type tool and a jig to make sure the job is done properly.
http://www.stewmac.com/freeinfo/Jigs/i-4043.html
It probably would be easier to fill in the slot and rerout - just make sure you find the same wood as your bridge to ensure a good finish.
I know you are not converting the saddle, but here is a how-to link.
http://www.frets.com/fretspages/Musi.../leftconv.html
Are you wanting a wider saddle to compensate the guitar properly?