El Mahdi
Muad'Dib of the Anauroch
Well, not quite: if the Warlord/Caddy/Marshal herself thus burns her action instead of doing something else she's not pulling her weight.
Sure, but it's just a temporary thing, maybe one round; that is unless the player of the Warlord continues to beat their head against a wall.
I'm betting that more than likely, players will probably tell the Warlord's player up front they aren't going to follow any of their guidance, and the player of the Warlord won't even bother with them.
Even more than that, I'm betting groups will collectively think about how to use the Warlord's actions before they actually give out them out - though it still remains the choice of the Warlord player on what to do and whether to even give up their actions. The player of the Warlord doesn't have to be an expert tactician, the character is the expert. I don't see a reason why the players can't discuss the tactics instead of leaving it up to just the Warlord's player.
I can also see players purposefully roleplaying that aspect of group dynamics. That can set up things like Han resisting Leia's guidance when they first meet.
It could be fun.