As someone who really doesn't like 'Sleight of Hand' as a skill because of how infrequently it comes up... reincorporating the concepts of pickpocketing and hiding things on your person back into the abilities to pick locks and disarm traps is a definite 'Yes' for me. Now whether that's by having Thieve's Tools or a Thievery skill... eh. Six on one hand, half-a-dozen on the other. Skills and tools are pretty much the exact same thing except Tools are like a non-magical Material Component. Lose the component, and you can't do the action.
Which I think is exactly why the items were split up... because they wanted the idea that you could pickpocket as much as you wanted, but that you HAD to use tools to open locks and disarm traps. I understand conceptually what they were going for... but I just don't see "fine motor skills" or "manual dexterity" nearly used enough to warrant having a skill for it. But you put lockpicking and trap disarming back into it... then you've got something worthwhile.
Agreed.
Also, I think that for opening locks and disarming traps, a wide variety of makeshift tools would be appropriate if a PC lost the tool kit. In fact for disarming traps, I would think that rocks and timbers and other such items not found in the toolkit should often be used, even with the toolkit ("Yup, that lever ain't gonna move with this wedged in rock in the way"). I think less of this for things like fine jewelry work.