Remember how earlier in HPMOR (chapter 47) Harry swore to take as an enemy whoever it was that killed Narcissa Malfoy? It was no an unbreakable vow, but the same principle applies. Not only was he very careful, with many conditions laid upon the pledge, but the first condition said that Draco could release him from the pledge at any time. There is no danger of a vow like that being not perfectly thought out, because if something goes wrong, you can just have whoever you swore it too annul it. I understand that getting a perfect wording is not trivial, but if you just keep a human in the loop like that, you can avoid most errors.

Harry is one of the most intelligent and rational people in the world, and took great care in designing that oath, (which, as you point out, is not unbreakable,) and he's still in a position for it to screw him over, since if Draco's father has been doing his best to change his son's sympathies, then Draco may not be inclined to release Harry from the Vow even if it turns out Dumbledore burned his mother for good reasons.

If Harry had taken an Unbreakable Vow, then even with the escape clause, he would probably be obligated to treat Dumbledore as his enemy right now, with no way to get Draco to release him from it.

There's plenty of danger in an imperfectly thought out vow, even if you add a clause that someone can release you from it. Having someone who could release you from your vow isn't much help if you're already dead due to having been unable to act in self defense, for instance. Supposing you have to go down to the equivalent of a local police station to get released from a Vow, I would suggest that this probably retains most of the problems of being unable to break the vows at all.

In a certain sense I am talking about them, as the whole thing started from a discussion of what would happen if we used a specific method to get around the disadvantage, but in practice I am not really talking about them, as with the downside basically gone, there is no real difference between them and an Unbreakable Vow like in canon, with no downside. In other words, I am talking about Unbreakable Vows with no downside, but that could either be the ones we were talking about (with the downside, but with it overcome) or the simpler version which does not have a downside to start out with, and it does not really matter which.

If you think it doesn't matter which, I have to suspect that you're not thinking very hard of the implications of the MoR method.

Not everyone can be easily imperiused, nor is everyone capable of casting the spell, and it is probably impossible for a single person to keep a large number of people imperiused at once (canon doesn't say whether it's possible to imperius more than one person at a time, but provides no evidence that it is, and if it were, we could expect people like Voldemort to make extensive use of this.)

If the people being used as binders are not controlled perpetually, then we have a segment of the population which is being victimized in what many humans would regard as one of the most abhorrent ways possible, being routinely mind controlled into performing acts to which they would not consent of their own volition. These people, to put it lightly, do not like the segment of the population which is doing this to them. The people exploiting them need to make arrangements to keep them safely under control, as with chattel slavery. If such arrangements aren't strong enough, they're likely to engage in violent uprisings (although unlikely to succeed if and when they do, they're less powerful and less well coordinated.)

Not only does the society have to invest labor and resources in keeping this segment of the population under wraps, any enemies who want to destabilize this society would do well to target this system. Kind of like the helot system, which was convenient for the Spartans in terms of productivity and military strength, except for the fact that any time they stayed away from home for too long, they were in danger of a revolt, and they had to make all the other city states they dealt with swear to support the system, since it would be so dangerous for them if anyone tried to destabilize it.

You can increase the security by keeping the people shut away somewhere, but then you lose the productivity of the people being used as binders.

Probably the most efficient method would be to force all the binders into unbreakable oaths not to rebel. You are, of course, still losing a significant portion of the total magical powers of the population by using unbreakable vows en-masse like this, and far from other countries seeing and wanting to copy this system, they're liable to see it as either an exploitable weakness or a human rights violation, in which case this society could be facing trade sanctions, embargoes, or even war.

And of course, you still have the issue of how society undergoes the steps to reach this point.