Ive been thinking and discussed this with other people.
We have our defend mission after we attack sometimes, which tend to turn into a bloodbath as no one is prepared.
so why not bring in a defend only mission, we get alerted 10-15mins before the attack, we move to that town, set up defenses around an already place hq, this can have at static launchers etc. and we have to defend the hq for 20 odd mins.
I think this would be a great idea as if CSAT slots get put in place, they could help attack the hq. it also allows those who like the defend a better chance to play the defend