Saddle slot in bridge too narrow
 

I have a mid-to-late 1970s Matsumoku-made Aria PW-70, which is a nominal D35 copy with solid Sitka top and laminated Brazilian (!) rosewood back & sides, with a full vine inlay on the fretboard; it is what I consider my "beach/camping guitar", being the only one I own that I'm willing to risk under such circumstances.

The guitar has been re-fretted...not the best job I've seen, as the tangs vary in length as they hang over the neck binding; I had to go along the fret-ends and round them off & do some leveling with a file but overall I got it quite playable and the guitar sounds great. This poor guitar has also suffered from a gawd-awful attempt at re-finishing the top, a condition for which I have a plan, but my main question is this...

The BRW rosewood bridge has a way-narrower-than-standard saddle slot and I'd like to replace the warped plastic (or whatever it is) saddle; I'm vacillating between cutting a new saddle to fit that narrow slot, with gawd-only-knows what result, vis intonation (it's fine as it is now) or trying to widen the slot to a standard size.

If you were going to widen the saddle slot, how would you proceed? Or...should I simply shave a new saddle down to fit that skinny slot?

"intonation (it's fine as it is now)"

In that case IMO just thin the new saddle to fit.

What's the current saddle slot thickness?

If intonation is OK now, easiest not to mess with the slot.

Slots are routinely routed on the guitar. That requires a router guide jig.

Like this or a do-it-yourself copy:
https://www.stewmac.com/Luthier_Tool...uting_Jig.html