If you have a spare ESP32 board, you could flash a VCON firmware on it which turns ESP32 into a remotely controlled programmer. Wire ESP32 to the XIAO’s SWD pins, and reflash XIAO - you could reflash any bootloader on it, or Arduino-compiled sketches.
If you’re uploading a bootloader, make sure it is in .hex format.
Wiring instructions are at https://vcon.io/docs/#seeeduino-xiao
ESP32 flashing instructions are at https://vcon.io/docs/#generic-esp32
If you keep ESP32 wired to XIAO, you could reflash your XIAO remotely at any time.
Disclaimer - I do represent VCON product. It is commercial, with freebie quota for first 10 devices, so reflashing XIAOs (and not just XIAOs) could be done absolutely for free.