Love your idea - anything that gets bunnies off wire mesh is a plus in my opinion
I wonder - why not use the 'escape areas' as well? Or are they actually used for something else, just dog proof?
Be prepared for the does to make and use their own burrows instead of the crates you have buried for them
make sure there is plenty of shade and shelter for them - one piece 6x4 might not be enough. and several crates above ground as bolt holes if a hawk flies over - rabbits are a bit naff from a survival point of view, just the shadow of a hawk can give them a heart attack if there is nowhere for them to hide.
Also, if you can, introduce feed plants outside that also offer shade and wind protection. You can cut armfuls and throw over the fence.
Plus TOYS!! they don't have much to do in there except eat and dig, so they will dig.... toys are easy - apple branches to chew, things to roll or throw around
You can see I am coming at it from a bunny welfare point of view, but I am sure you want to have happy bunnies as well as safe ones