CTF would be great for Harassers. The only thing is whether it's done like most CTF gametypes or more like a Carry the Flag gametype, where dropping your own flag means you have to manually return it to base instead of just touching it to send it back.
In Unreal Tournament, for example, the default is the touch-teleport mechanic, but with the Carry the Flag mod, you not only have to bring the enemy flag all the way home, but you have to bring your own back to base if it's taken as well. However, this also means you can cap mid-field AND you can deliberately take your flag away from base and into the field to cap away from home to intercept a friendly flagrunner, but that of course is a big risk if the enemy gets you and takes your flag. It's a total blast in UT; I can only imagine how crazy it would be in MWLL.
Would absolutely require special maps, though, to prevent someone in a Heph from driving off into the sunset on Mirage, never to be seen with the flag again.