As a point of reference, we ended up doing something similar but in our case we managed it as outlined in this thread - rather than changing the uboot environment I elected to make a script that manages overlays.txt on the fly by appending a variant-specific DTBO file, which is fully achievable within the current confines of TorizonCore builder.
But I would be very interested in an official mechanism to support this sort of dynamic hardware configuration if it becomes available, be it via either run-time selection of a particular full DTS file or just dynamic selection of any additional overlay(s) to apply. The base mechanics are already in place as done using the toradex config block logic to do carrier board/SoM variant detection; enabling the HW developer to extend this with additional definitions might be a very nice/clean way to do this.