If you're into craft beer there are plenty of good examples of fruit lambics out there.
I've tried loquat lambics before, and while good, the point in my mind of a lambic is to introduce tart/tannic/acidic character like with cassis or raspberries, or alternatively dry aromatics like white peach.
There are loquats with strong aromatic character, as well as mildly tannic (astringent) ones, but I've never sampled a lambic prepared with these types of loquats. The usual loquat type which is what the brewer most assuredly had on hand tend to be mild but balanced, which means they have little to offer as a brew highlight, and are much better used in a preparation that highlights the fruit itself with specific focus to the delicate balance already present as well as the soft pulp texture. Loquats preserved in agar are my favorite.
For persimmons, there are plenty of good examples of fruit out there with strong tannic character and some aromatics (California Maru comes immediately to mind, but there are others), so certainly there's potential for using them to make a nice lambic addition.