I’ve seen people commenting about large prints and worrying about running out of filament. With the active filament running past a suitable sensor or switch it should be possible to automate the splicing on the next spool. Or at least sound an alarm, pause the print, move the head up a little so the print isn’t spoilt and then resume when a splice is done.
https://www.artesea.ch/products/technology/3d-filament-splicer