Lockpicking and pickpocketing do not require any Scoundrel talent. There is no link (except maybe classical roleplay).
The only ability that has strong ties with the scoundrel is furtivity, as it allows you to hide in shadows for minimal AP cost, which then allows you to make powerful strikes (I've heard this kind of gameplay is also possible for a marksman).
So, yeah, lockpicking and pickpocketing can find their way in a wizard's repertoire, alongside sneaking.
Pickpocketing is very lackluster, and would only shine in the very early game (when you are broke). But in the early game, it's not a good idea to invest in pickpocketing anyway as it gimps you.
Lockpicking, yeah I guess one could invest one or two points in it, and keep items that provide a bonus in lockpicking. But as Stabbey said, there isn't much to do with lockpicking in the game (so it's easily considered wasted points).
Sneaking, honestly I'd just go with a few points in Aerothurge, and use the invisibility spell instead.
I think one doesn't need much ability points anyway in this game, so you can absolutely invest some in lockpicking and sneaking if you desire so. I'd avoid pickpocketing in any case. Lockpicking has a very progressive return (as, similarly to loremaster, you encounter harder locks as you progress through the game), but sneaking is either 5 points in it or none at all (maybe 4 or 3 depending on your traits and your boots).
