You have put some time and effort into this so I will be gentle.
Thanks but such paternalism is neither necessary nor warranted.

I ask you again to start at the beginning.

It is the politicians who decide to intervene and generally place a whole string of limitations on such intervention....
Yes, when isn't that the case? I don't see how that is relevant to my analysis.

So all that said ... don't plan for options you at your level will not be asked to decide on.
Have you heard of contingency planning? Maybe it's different in your neck of the woods, but I've participated in lots of planning for contingencies that were unlikely to materialize for whatever reason. In fact the vast majority of war and contingency plans I participated in were never executed. Again, not sure how this is relevant to anything I wrote.

So if a guardian angel starts to take out 1,000s of the bad guys (being from Assad's political and military hierarchy) is not the same as killings civilians (men, women, children) in Homs with artillery, mortars, armour and then by firing squad.
and

Sadly though he seems to have influenced your thinking because you come up with this: "None of these options sound very good to me and they would all involve killing a lot of Syrians, not protecting them." So think it through again I suggest and understand that to save Syrian civilians a lot of "bad guys" are going to have to be killed.
If you look at the problem only from a short-term, tactical perspective, then yes, stopping the killing appears to be a straightforward goal. And just to be clear I do think that stopping the killing is both noble and righteous and should seriously be considered. My default position i that I want to do something about it. However, experience has taught me that it is, unfortunately, not possible to put such "tactical" political goals in a nice little box and isolate them from everything else that is going on to include the longer-term effects of expediently satisfying the short-term goal. Looking at the potential long-term and "big picture" effects and how things might play out was the purpose of my post.

Secondly, while the political goal my appear simple, the execution is not straightforward since it's not easy to distinguish the "good" guys from the "bad" guys and civilian deaths can't be completely avoided. Therefore, any intervention is very likely going to carry a cost in civilian deaths caused by the intervening force. Depending on the type and scope of the intervention, and how things turn out, an intervention could easy kill more civilians than are "saved." The military instrument is quite blunt when it comes to "saving" civilians.

Finally I suggest that your "gut feel" is not what counts here.
My post was a combination of facts, analysis, judgment and opinion. If you didn't like the opinion part, then feel free to ignore it.

When you arrive at what you think will or won't work consider the basis on which you arrived at that decision. In appreciations the deductions and conclusions are not 'plucked' out of the air but are arrived at through your discussion of factors. So "in my opinion" and "but I think" and "the odds are" have no place in an appreciation.
My deductions and conclusions were not "plucked" out of thin air. They were arrived at through my "discussion of factors" and are not merely my "opinion."