Crossfit Endurance has WODs, most at least contain some monostructural training.
can you use weighte back pack or farmers walks? that might make things a little more spicy.
Generally CF Endurance discourage from using treadmill, but aside from the time it takes to speed up, i don't see any issue. i generally do a 1k every day and a 3k when i feel i need a little more (with and without loaded backpack). interval stuff, i keep off the treadmill.