i like this idea, its sounds like a great idea.
like that one on the link too...
i've done somethings very similar before. but usually with just one pallet, and then built a raised bed on top. or cutting them up and nailing the pallets together to make the edge and bottom of raised beds.
i also have done some stuff taking the pallets apart and then using trees cut down for posts, and the pallet
wood for a simple fence/trellis/fedge.
i was working with similar thinking when i was working on this fence, which is made with willows, pallets and some salvaged free wood:
https://permies.com/t/16172/projects/living-fence-project#208940
theres some places where pallets are underneath or edging the beds, and theres a lot of woodchips, branches and leaves underneath the soil in those. some of the boards were nailed right onto living trees.
i am starting some new fedges =) here ...since i have moved....just in the past few days i am beginning a new small fedge..
unfortunately not a lot of pallets to be found here, but i did bring a few....not much to do a bigger area.
fortunately though theres lots of wood around, theres also tons of cherry plums, so thats what i have been starting with.
going to start a bigger one soon in a different area, just planning it out now....starting some new trees and plants.