I've actually been contemplating a variation on this.
A trench dug just wide
enough to allow the target plants [I'm thinking 10-15 foot wide pomegranates and citrus, perhaps a few more exotic subtropicals as well [along with guildmates under their canopies], in small clumps by species, say 3 cultivars in a row of species X, then 3 of species Y, etc] branches to spread well, running east-west. The south side is sloped in to the
trees at an angle shallow enough to permit full sun for the full duration of the ripening time [which is a good reason to avoid winter-fruiting citrus, there are cultivars out there which ripen during the normal early autumn months. At my latitude I certainly wouldn't want anything that would need ripening after Halloween.]
Above them is a reflective insulated ceiling of some sort, on hinges to change the angle throughout the growing season, situated at an appropriate angle to funnel additional light into the plants during the start of the rainy season as they're finally ripening, giving somewhere between 150 and 200% of the actual sunlight coming through the atmosphere to the plants.
With the right cultivars this setup may not be necessary, I'm going to be experimenting directly with simple microclimate hacks first but given our limited autumn
solar gain I'm certainly having my doubts. My best bet is getting the very earliest ripening cultivars I can get my hands on and doing the microclimate hacking to punch our ~75 degree average summers up into something more comparable to ~90 degrees within the growing space of these particular plants, so hopefully they'll ripen before the mid-september cloudcover sweeps in.