If extended use is a requirement one option is this: https://www.tethertools.com/product-category/power-management/
I have two of them. I got them for long shoots with Sony A7RII where camera was on tripod for several hours shooting architecture for blending.
They make a unit for the XT-2, etc. battery box. I've shot several weddings with XT-2 without having the battery problems mentioned. Always over 1000 images, generally fewer than 4 batteries. Shooting real estate, using the LCD for composition and bracketing I get fewer images per battery but still would work out to more per battery that the OP. I have lots of off brand batteries and haven't noticed a significant difference. Even though I got a connection to XT-2 for the Tether Tools system I've not used it yet.
