I'd try backwards-bent rods first, it's simple, reversible, actually you can do it yourself.
If this doesn't work, perhaps compression fretting will. This is something you would have to discuss with you luthier. The frets are removed and replaced with fret wire with slightly oversized tangs. This will give the fretboard a back-bow.
Sometimes the wood at the body end compresses, and the acorn nuts sink too much into the hole when the adjustment nuts at the headstock end are tightened. John Hall suggested a few drops of Super Glue to harden the maple under the acorn nuts. This should be done in 3-4 applications, letting each dry before the next application. (Needless to say, remove the truss rods before doing this!)
Your luthier could also try heat treatment to correct the bow. Or a combination of any of these methods.