There are 3 outcomes to the mfm
1) it is the greatest thing ever
2) the reality falls way short of the fantasy
3) it damages your relationship
So 3 outcomes - 2 of them are not good. Again it works for some people and we hear about it here, but then again a lot of the ...... on the forum is bullshit (so be careful).
I don't disagree with much of what you've said. It is good to be cautious and understand that the reality may not meet the fantasy.
At the same time, it's kind of a straw-man argument to make a 3 point list and then say because 2 of the points in your list are negative, it is very likely you will have a bad experience even though the number of points is kind of arbitrary and there is no consideration of how likely any of them are relative to the others. If you added another point for "it was a fun unique experience but not amazing" would that make it even? What about if it strengthens the relationship because you do have some hurt feelings or misunderstanding but then you work through it and reach a knew, deeper understanding and appreciation of one another?
Again, just playing devil's advocate here. There is inherent risk in this and anyone should proceed cautiously. I think though that it is a lot more complex, nuanced and specific to each relationship, than a simple reductive calculation of potential outcomes.
There are some stories on here with negative outcomes that I've read - or others where it was a negative experience followed by growth and then a positive experience.
Many of the negative outcomes also seem to be largely due to a poor relationship to start with. If your relationship isn't solid, I think there is a lot more potential for this to damage it further. I also think hotwifing, with the wife going on dates by herself, is way more inherently risky than a MFM threesome.
Ultimately though, only you can really evaluate whether you're ready or not and as XTac says, if you're not sure, probably best not to dive in. Maybe you can test yourself with some smaller steps, like having your wife flirt with someone at a bar / dance with someone while you watch. Then she returns to you and you both go home and have hot sex.