I've always found it interesting/weird how bikepacking seems to have a different 'style' than touring or utility cycling. Like using an overgrown seatpost bag instead of a rear rack and panniers, for example. I guess maybe it saves weight(?) and that could be important if your bikepacking route involves hilly singletrack or something, but otherwise I feel like the more traditional ways of handling cargo are more versatile.

I was thinking in a similar way, wood plank secured to the existing one for the occasional larger load, then taking it off when not needed.