I can't say I've ever had a player attempt to abuse the spell, but this thread has made me think about it.
Let's start with the spell description, trying to keep everything to the RAW:
QUOTE
The caster seizes control of the target’s mind, directing everything the
target does. The caster mentally gives commands with a Simple Action
and the target is compelled to obey.
Well, the fact that the caster directs everything the target does rules-out the guard opening and closing door example above. The caster controls everything they do, that doesn't mean that they can do what they want when they have a free initiative pass. It's also arguable that, once under the effects, the target would stop doing anything until ordered to do so. If the spell is in effect then the target really does nothing unless the caster commands it. If you subscribe to the stupid school of RAW then this may also include breathing, but in that case characters may have died long ago when they forgot to declare that they respired as usual within a minute of starting the game.
There is no mention of attempts to break out if given a suicidal command, and no mention of bonuses against commands that don't fit with the character. As such, the command 'commit suicide' would be executed to the best of a character's ability.
Now I've got to say that this is certainly very powerful, what I'm not certain about is if it's balanced by the drain code of the spell. The big issue seems to be that people can't defend against it, to which many have mentioned the possibility of frequent background counts and similar. That strikes me as a nerf to mages in general, however, and doesn't really address the issue with mental control. Mental control is still going to be the best way for a mage to take someone out, as his other spells are just as gimped and still less powerful (drain issues aside).
As for effect, it's perfectly possible to kill someone with a force 2 control thoughts. The drain for that is 3, which is the same as a force 9 stun bolt. Both are probably gonna take the opponent out with one net hit, but one is specifically a combat spell and deals physical drain whilst the other is general and deals stun drain. In this case I'd have said that, to stop control thoughts from being a better combat spell than a combat spell, I'd have said that an extra resistance test should probably be allowed. I don't want to remove the versatility out of combat, I just want to remove the in-combat advantage over the dedicated combat spell category.
Commanding a guard to open the door is not, however, something I'd allow an extra roll for. Opening that door is probably something the guard does every day, several times. If he's aware he's being commanded he's gonna be fighting every command. Commands that his survival instincts object to are gonna be fought more than others, which is why when people planning to commit suicide go to high places they stop when they think "blimey, that's a long way down".
Personally, for the versatility offered by even one command, I'd add the 3rd edition threshold of 1/2 willpower back into the spells. This means all but the most weak-willed individuals have
some chance of resisting. For the average willpower 3 character, 1/2 willpower is only 1 hit which a competent mage can deal-out, but it at-least means a GM can boost an enemy's willpower to the point that it's unlikely to be mind-controlled (with drugs, ETC).
I'm also a fan of stigmatizing mental manipulation spells, much the same way that rape is stigmatized today. People who've been mind-controlled will be disturbed by the ordeal, and in many cases develop similar mental problems and need therapy. There will be people who've been mentally controlled to do something, and not punished as it obviously wasn't their fault, who then go on to commit crimes and claim someone mentally commanded them to do so. If you make it clear that the NPCs are people, and the PC is still doing this despite the obvious harm he's doing, then there's an argument for the character to eventually become a magical threat in their own right.