At some situations we pretty much needed to actually enforce the other - that they should also take backyard villages after advancing on hostile territory if we don't want to run out of defenses.
However, we have never tried enforcing it on an individual level, just keeping it balanced for regions or front lines. In every tribe there are players who are temporarily short on time or having other issues and can't actively fight on any front for some periods, so it's pretty easy (and logical) to specifically ask them to spread in the backyard and create D villages for frontline support. So long they are team-players, it is useful, as this strategy allows the warmongers to continue fighting on fronts instead of backyard cleaning, and allowing the time-stressed members to remain useful for the community (thus eliminating a couple stress factors on both types). However, it requires some prequisites like an appropriate player mindset, that's something a good tribe should be looking for before recruitment anyway or should have it's learning curve designed to make the new recruit adopts it.
