I will be really annoyed if they merged it with sneak... that would be like merging heavy armor and 1-handed weapons. Makes no sense.
I'd be really annoyed because it would then seem like Sneak and Security have basically the same sort of options as in Oblivion. After all, if there's a combined skill, then there'll probably just be perk trees for stealth kills, for reducing armour penalties when sneaking, and for lockpicking/disarming traps. That would be pretty disappointing. I would have liked to have seen more content put into Sneak and Security and keep them separate skills. Perk trees for Sneak could include: stealth kills, reducing armour penalties when sneaking, pickpocketing, ability to use magic and remain undetected, and so on. It would also have been nice to see Security expand into a more general "Thief's Tools" skill, where it's not just lockpicking and disarming traps, but perhaps also cutting glass to enter houses/castles through windows, and stuff like that.
As for lockpicking, I always just used auto-lockpick because I found the mini-game too easy. Sure, I might break a few lockpicks on the harder locks, but it was never a big problem. I'm not opposed to a minigame, but unless it's fixed, I'm inclined to agree with those saying that it should just be removed and make lockpicking a dice roll based on player skill.
The trick is to design the minigame so that it gets easier as your character's skill increases, but that it's not the sort of game where even locks which are very hard relative to your character's skill are easy to pick when you, the person playing the game, have had enough practice. I'm not a fan of giving some locks a skill requirement to even attempt.
Some suggestions (these are based on keeping the same style of minigame as in Oblivion, where you need to lock in the tumblers one by one, and higher skill = more tumblers stay in place when you break a lockpick, and tumblers move more slowly, and higher rated locks = more tumblers).
1. Don't freeze time. But don't make it real-time. As it were, "dilate" time, at a rate which depends on your character's skill. That is, for character's with a high security skill, the lockpicking minigame basically happens when the rest of the world stands still. For character's with a low security skill, the rest of the world happens at normal speed while you are trying to pick the lock. The idea here is that with a highly skilled character, you can wait until you are out of sight, and then try the minigame as long as you like. But with a low skilled character, even you enter the minigame when you are out of sight, you've got a good chance of being spotted while you are trying to pick the lock. So if it's a harder lock, then you can have a go when you have a low skill, but you need to work fast (you might rush the minigame a little more, breaking more picks).
2. The speed at which tumblers move needs to be more highly randomised and unpredictable. Not just faster and slower. But as you increase in skill, the tumblers fall at more regular rates.
So those are ideas to make the game more difficult. But probably the
biggest problem with the lockpicking minigame in Oblivion was that there was simply no cost to stuffing up. So if you were a low skilled character, you could try a hard lock, and if you didn't manage to open it, oh well, get some more lockpicks and try again. This meant that there was very little discouragement for trying locks that were very hard, relative to your character's skill. So some ideas for how this could be fixed:
3. Make breaking a lockpick noisy. If you break a lockpick, then, depending on how close an NPC is, they might come to investigate because they've heard something odd.
4. Perhaps breaking a lockpick in some way also damages the lock's mechanism, which then makes the lock harder to pick. There are number of ways this could play out - apart from just some tumblers falling. (i) Increase the rating of the lock, so that, building on idea 2 above, the tumblers fall at a more unpredictable and random rate; (ii) A tumbler can get "stuck" in the wrong place, so that you can't push it up into the right position, as you normally would. To fix it requires being at a sufficiently high security skill. (iii) I'm sure there are other possibilities.