Update!
Brewed this a couple week ago. Ended up as 1.073 OG to 0.998 FG, with 33IBUs to balance. It's cold crashing now but tastes good so far. Nicely dry, the white wine comes through, but it's definitely beer. It's not too tannic.
I brewed 13 gal of 1.059 base Saison (30% pils, 30% wheat, 7.5% Munich, 2.5% Caramunich, 30% reserved for grape sugars). Hopped with Pacifica, pitched WLP590 at 70F until 50% attenuation, then raised to 74F. The 30% fermentables balance was calculated from 1.125 SG wine concentrate, where I added 3.5 gal after the fermentation had hit 75% attenuation. Held it at 74F and after 72 hrs we'd hit 0.998.
Probably gelatin it at this point, then run off to kegs
Sounds delicious! I've seriously got the itch to brew this again lately. I'd like to keep it in the low 5's for %ABV this time, though. I'm hoping to get an easy-drinker, but without watering down the wine character, either.