Making three of your majors, the ones that you will use all the time, come from just one Attribute, tends to gimp your character. It's good if you know what you're doing, but if you don't, you could be crying for a while in the teen levels.

This is true.
Hmm for the security thing, You could grind with the Skeleton key, run around all the cities unlocking all the doors(Almost every door to residence places tend to be locked) don't know if they lock again after three days though, then going around dungeons and opening things there, and since they do respawn every three days....
Sorry I can't be more help :/.

Security leveling love comes from visiting the Aeylid ruin of Wendir and then returning in later days. Everything, I mean everything needs a lockpick.
As for the Skeleton Key, in my experience I've found that it slows my leveling, as you also get experience when you break a lockpick. Not sure the exact calculations, but I can see a visible increase every time.
I'd dump the Skeleton Key.
If you're looking to spam, and I'm pretty sure you're not, but just in case, use a lockpick on a lock that is a high level for you, say hard, get the first two tumblers, then back out. Start again, then back out. Rinse and repeat for fast spam action.
My mage opens only by spell. He has a case where he can carry 10 lockpicks, for very hard locks, as he doesn't have that spell yet. If he runs out, gotta come back some other time, that is, if he remembers.

Thank you all for your input, both on the subject of 3 majors tied to same attribute and notes on security in general.

I made a "test" character last night with speechcraft as the third active major, rather then security, and tried it out. To be accurate, speechcraft is the third major that will be used to trigger leveling, when I'm ready, or after sneak and marksman are capped. It works well. Marksmanship and sneak drive leveling, which is great. Those are the skills my character needs the most and they reflect the way I will play. Since only two skills are driving leveling they both rise nicely. (I can readily imagine how three skills tied to the same attribute, without some very careful minors leveling, could trigger problems later. Thanks for that tip!)

For custom class name, I'm going with Arcane Archer.

I'm likely to play Kira at least a little differently (if not a lot differently) than Acadian plays Buffy, so a subtle different in class name is called for. However, thanks Acadian for the PM with class name suggestions, and permission to use MysticArcher if I so chose. I appreciate it!

Oh, and Big Daddy, thanks for the suggestion on locks (starting hard and very hard locks then backing out before last tumbler). That's a very clever suggestion.

However, you are right: I don't like to spam. That's why I try to pick majors that will reward me well at level-up time just for playing the way I like to play that character.