I'm assuming that they initiated a Plan B when Maggot compromised the mission.
Was the original plan to go inside and machine gun the officers?
Were the grenades down the air shafts plan part of the original? And if so, why were Maggot and Jefferson to go inside the chateaux, risking exposure if they were just going to blow it up anyway?
The initial plan was simply to storm the building and kill as many officers as possible with gunfire, grenades, etc. The plan seemed to be to sneak some men in on the first floor, and hit them from there and the ground at the same time. Everyone turns to face the ground attack, and troops coming down the stairs hit them from behind.
Dropping grenades and gas into the shelter and burning it out was improvised on the spot.
-- If I could stop a rapist from raping a child I would. That's the difference between me and god.
Yeah, the plan was to sneak in, disable the communications at the chateau (phone, radio), then use surprise to kill as many generals as possible, then get away before the infantry division nearby could react. Maggot screwed it up.