So far I've been focusing on my Sneak and Archery trees, but should I also put a few points in Light Armor? Or would that be pointless since im not supposed to be seen? I do find it easy to pick 'em off from a distance unnoticed, but there are the occasional fights were I have no choice but to melee.. Also, will I be able to put points into the Lockpicking and Pickpocketing trees, or is that just spreading my points too much?

I'm playing the same type of character,sneak and archery.
While I'm wearing light armor I don't intend to put many perks in it.
I will be putting my perks in sneak,archery,alchemy and maybe pickpocket.
I'm only level 6 at the moment so this may change but I haven't been in enough close combat yet to worry about the lightarmor perks.