Also, as far as the sneak multiplier goes for shortblades, here's my logic. While you can obviously get a good strike with a sword when sneaking, there are many less ways to do it, as well as making it quieter. First, just imagine trying to thrust with two weapons, the first a longsword, and the second a knife. It is harder to aim the tip of the longsword at a specific point because leverage is causing gravity to push the blade down from the fulcrum of your hand. A knife is short enough to negate this. Also, knives can easily be drawn across throats, or used to stab the chest from behind (by gripping your enemy and pulling the knife towards you)
I'm still not really sold. I agree that you're going to be less accurate with a big sword rather than a dagger. But so what? You can just swing the big blade at the enemy's head and chop it in half - there's no need for subtlety when you've got a big heavy chunk of metal.
Maybe the thought is that better armor will better protect against brute strength, so that's where the accuracy of a dagger comes into play - being able to accurately stab into a weak spot between armor plates.... But it still seems that for the most part,
provided that you can approach undetected with either a longsword or a dagger, you'll be able to perform a "critical hit" equally well with either.
Then again, I'm not exactly sure what matters here. You (along with many others) claim that the damage bonus for sneak attacks with a dagger should be greater than that for a longsword; I suggest that perhaps it would be more credible to make sneak attacking with a dagger more advantageous because it's easier to get within striking range whilst remaining undetected. But I'm not entirely sure how this difference would look in game. On my proposal, on average, you'll get in more sneak attacks with a dagger than you would with a long blade (because you'll be detected more often with the long blade), which means you'll be forced into less combat time with a dagger than with a long blade. On the other proposal, you'll get in the same amount of sneak attacks, but with a higher damage bonus for the dagger you'll tend to kill the enemy more quickly, which again might mean less combat time. So it's not clear to me that there's a big substantive difference, in terms of how this will play out in game, between the two proposals.... Which is not to say that there's no reason for choosing one over the other - I just don't know what it might be.
That has nothing to do with them being separate skills though. If a dagger does 1d4 damage and a long sword does 1d8 all else being equal there is no reason to use the dagger, having it be two different skills just means there is also no reason to take the dagger skill. You have to give a reason to use daggers totally separate from the issue of how many skills it should be represented by.
Good point. Some possible reasons for picking the dagger skill over the long blade skill: they are governed by different attributes (so you pick a skill governed by an attribute which also governs other skills you regularly use); there are differences in how they are needed for advancement in guilds (you need a high dagger skill for Thieves Guild advancement, but a high long blade skill for Fighters Guild advancement); faster rate of skill increases if you've chosen the stealth specialisation rather than the combat specialisation (but this is not so good a reason: forgetting the other reasons for the moment, if you took the stealth specialisation and took long blade over short blade, this could feel like the game is punishing you for taking the better option).
Also, just one final comment on the damage per second remarks. It's true that daggers will do more strikes than a longsword over the same duration. But I don't think (and I'm not saying that anybody is suggesting this) this should be used to justify claiming that daggers should do, over time, pretty much the same amount of damage as a longsword. After all, the major benefit of going for the longsword is that it does more damage - and this needs to be not merely
per strike, but over the course of a battle. If that advantage is taken away from longswords, then we'll start complaining about how long blade is a much poorer choice than the other weapon skills!