Bodyguards is the very opposite of versatile. It also does very little to deal with any threats, because the odds are the target we are guarding is not going to be the target of the vampire, so the vampire can kill dozens by the time he happens to go for someone we are guarding. Guarding sleeping dwarves in general is far more likely to catch vampires, which is why it works better as a concept.
Bodyguards are more versatile than specifically guarding one particular dwarf, exclusively while they sleep. Period. Presuming the average citizen sleeps in a dorm, and thus is safe from vampires, this suggestion is as good at combating vampires as bodyguards are, but only protects a dwarf while they are sleeping, other threats are not covered, thus it is less versatile. No matter how lacking in versatility you view bodyguards to be, they protect against more than just vampires. Presuming instead that all dwarves have their own bedroom barring the militia who have a barracks, then depending on how synchronised your dwarves' sleep cycles are, you may need anywhere between 16.5 and 50% of your population watching the rest of them sleep. That's a minimum of 33 sleepytime guards if your population is 200, not even accounting for the time spent while the guards themselves sleep, vs a dorm and however many bodyguards as you have nobles with bedroom requirements, which is a max of 7.
They are following a civilian, the civilian can be expected to flee from danger. The bodyguard is better employed to chase after the danger than to follow after his charge. If there are multiple enemies, the bodyguard dispatches one of them, he will then try to return to his charge, which might be on the other side of the fortress by now. This is the dispersal of forces/defeat in defeat situation at it's worse, a lot of people running about between contradictory orders.
Civilians are currently about as likely to flee from danger as they are to engage in fisticuffs. Military dwarves automatically attack threats regardless of current orders, it seems unreasonable to say that bodyguards wouldn't do this just so that you can say they would be bad. If there are multiple enemies, they will likely all attack the bodyguard, which might kill the bodyguard, but it'll give their charge time to flee and give your militia time to arrive, but even if the enemies don't gang up on the bodyguard,
you can still give orders to kill the lot of them, dwarves ignore schedule when given orders, overwrite old orders with new ones, and yes, you can give a single order to kill multiple creatures, so it works no matter how bodyguarding is implemented,
you cannot have contradictory orders, that isn't how the game works. Even if you don't give that order, they will also engage any threat on their way back to their charge.
You built an insecurable fortress, which is your fault. You can always build walls to create chokepoints and close off old mining tunnels or the ilk.
Except I didn't build it, every worldgen fort is like this. Try a reclaim and you'll see for yourself. I also described a fairly reliable way to secure it, by combining patrols and bodyguards, provided bodyguards are added in.
At the moment the dwarves have a massive advantage over goblins. But that is a problem that will presumably be fixed.
Then you're forgetting your fantasy tropes. Goblins are
supposed to only be able to win through sheer number and/or devious plots. Dwarves are
supposed to be better skilled craftsmen, giving them better equipment, better skilled strategists, giving them the upper hand tactically, and better skilled martial artists, giving them the upper hand individually, and that's without even mentioning that the dwarves are defending a fortified position, which boosts tactical advantage massively. Granted the goblins are a little too weak atm, cause they're not armed or armoured in their best stuff, and usually there isn't a single goblin that has armour on every body part, but they will never be on equal footing with dwarves, meaning dwarves being a few moments late to a battle with goblins isn't really ever going to be a big issue unless you've seriously dropped the ball on equipment and training.
If the mayor dies there is automatically a new election and a new mayor. I agree with you, at some point leaders won't be so easily replaced, at which assassins will make sense and then bodyguards will make sense (in that order).
That you don't know the strength of an enemy force, is an ideal state for that enemy. This because it guarantees that they will either overdeploy their forces, at which point you are unable to attack but you don't need to because you have tied down a greater quantity of troops with a less quantity. Or they will underdeploy their forces, at which point you can easily dispatch said forces and then take whatever it is they are guarding.
The enemy are going to know they are there as soon as they do anything. Ideally they know that they are there but not enough to actually eliminate them altogether, that is because as already discussed having to guard an indefinite number of targets against an enemy of indefinite strength can potentially consume more resources than the assassins would do *in* the time before they slipped up and were located by the enemy.
If you guard everything well enough we get to the point where the assassins do nothing at all, but them doing something is the best way to catch them. As long as they are there, you have to guard stuff, but the guards subtract far more from your strength than the assassins did the enemy's strength. Because one group of assassins can go after multiple targets, all of which need to be individually guarded with an equivalent amount of strength. So if the assassins can attack 10 targets, that means we need to have to deploy 10X the strength of assassins to thwart them; the trick is to find ways to guard multiple targets at once or stack your targets together in one location.
Is that future buff to nobles before or after the future buff to goblins? Anyway, the next election is not immediate, there is a period where no nobles can be assigned, it's expedition leaders, which do the same job but only in the smallest of fortresses, who are replaced the very same tick that they "go missing".
Yes, not knowing the strength of an enemy force is advantageous for the enemy, it doesn't guarantee over- or under-deployment, but it makes it
very likely, I'd use the phrase "all but guarantees" myself.
Even more advantageous for the enemy, assuming that by "the enemy" we mean assassins, is that they will likely be posing as visitors so that they can come and go as they please, meaning, contrary to your claim, you actually don't necessarily know that they're here once you find a dead body, you just know that they
were here. They
might have another target in the fortress and may have stuck around to take them out too, or they might have finished their mission and returned home.
So really, you kinda gotta either catch an assassin in the act, or not catch them. How's best to catch them in the act? A bodyguard's how, just one per potential target will do for catching them, if multiple assassins attack and overwhelm the bodyguard, good job you just identified multiple assassins, now send other militiadwarves after them, if they're lucky the bodyguard might survive long enough to be rescued by said militiadwarves and receive medical attention.