Control is actually EASIER to show and track (i.e. requires zero extra bookkeeping or tricky counter placement) "my" way, since a corps in an ungarrisoned enemy city area is automatically assumed to be controlling the city, and you therefore don't have to remember whether it is in or out
?ungarrisoned?, ?enemy? city area; 7.3.3.3.2 does not mention these things at all, you've just added them. In fact, you've mentioned the _only_ instance when "your" way would be easier. As soon as there's more than that single corps in the area, things already get confused. And you'd _still_ have to remember if it is in or outside, for if it's inside, that will definately affect your opponents' movement.
In the case of guerillas, if the guerilla were in the city then they would be beseiged by the corps... the only way that guerillas can co-exist without combat in the same area as a corps is if they are NOT in the city, and if a guerilla were to move into or be created in the same area as an enemy corps they would not be able to be inside the city anyway, since the city is already garrisonned by the enemy corps! It's really just less complicated.
There's no reason for a guerilla to be inside a city or for the corps to besiege it if they don't want to. Besides, the corps might not be allowed to besiege the city.
I don't think you're getting the problem. It's rather simple. Almost a joke: A Guerilla a Cossack and an Au corps are in the area of Barcelona, which is inside Catalonia which had been ceded to France. There's no garrison in the city. Now a Tu (not at war with any of these powers) fleet wants to enter the port. From whom does she need permission to enter if Tu already has access to Fr?
According to your interpretation of rule 7.3.3.3.2, all three units are now "acting" as garrison to the port. That gives them all control of it, so Tu would need permission of all three.
10.3.3. is quite clear in referring to garrisons (check the glossary) and not corps acting as garrisons by way of 7.3.3.3.2, and in any case it does not matter because any neutral corps in an area where an attack has been declared must either withdraw or DoW, so the situation you describe would never arise. But nice fishing attempt.
Well, since you took the bait.

...
Ok, I can accept THAT!
So... the same is true whenever any other rule mentions a garrison? Our argument is now moot. For the rules clearly do not give any powers to "Corps _acting_ as garrisons" anywhere, only to "garrisons". Are you starting to see my problem here? Either the corps is a garrison or it is not. You can't say it isn't when you don't like it. Off course, you could say the corps can _choose_ to act as a garrison, but that it doesn't have to.. Well, then we'd need a way to keep track of _that_, so that's where things get overcomplicated...
BTW: no attack was declared, just a siege.
Well again I protest that adding an extra layer of rules and being required to track the state of every corps at all times WRT to in or out of a city does not in anyway make the game simpler.
Strangely, we agree on the goal here: the awnser to this must be the simplest solution. I believe the simplest solution is the one where the control of a city is always clearly descernable by the the nationality of the counters on it's mapsymbol. You believe the simplest solution to be the one where there is the least need for players to bother themselves with such trivial matters as leaving a garrison.
But let's stick with the rules...
7.3.3.3 GARRISON FACTORS says that garrisons are "represente by counters of the appropriate type on the city or depot concerned"
7.3.3.3.2 tells us that a corps counter can be uses as a garrison. It just says "corps", but a corps is a counter (and nothing else) by definition. *I* would naturally assume that such a corps would be placed opn to of the depot or city as well. You think differently. My problem is why do you assume that 7.3.3.3 does not apply?
regards,
Ragnar