Is it possible to sneak up on dragons? Are there any types of enemies that it is impossible to sneak up on, even at high levels?
Now, the following skill trees can all help with such a character - smithing (higher damage daggers, good armer protection even if you have no/few perks in armor), enchanting (skill enchantments, elemental damage on weapons), alchemy (restoration potions, skill enchantment potions, poisons on weapons), illusion (make sneaking easier, paralyze, etc), one handed.
Now, as far as damage goes, it occurs to me that stacking every possible damage enhancement (including poisons/damage enh might be A) Overkill (congrats, you just did 2000 damage to an enemy with 1000 health. Yay), and

So, I'm trying to decide between all the options.
I'm kind of thinking about perking:
*Early concentration in smithing (both armor and weapons will be better)
*Wear light armor (easier to sneak)
*Sneak
*One handed
*alchemy with a focus on poisons (just feels more assassiny to me, and also give me access to some healing)
*Illusion (for muffle, etc)
Is that spreading Perks too thin? Alchemy tends to need a lot of perks - at least if you're not going to cheat and go lookup potion recipes on the web instead of actually taking the perks that allow you to identify effects by taste).
I'm thinking of putting basically no points into armor skill (if I'm doing it right, I shouldn't need too much defense, and the smithed armor should give me some survivability combined with alchemy). Eventually, if I get to high levels and start to have some free perks, I'm thinking pickpocketting and speech. Also, with regards to smithing, I'm not sure how high to perk it up - all the way up the light-armor tree, or just part way up, and save perks for other skills)?
As for stats at level up, I'm thinking no magicka, and a 2:1 ratio of health and stamina (that is, level health twice for each level of stamina). I mean, since you can use power attacks if you have even a *tiny* amount of stamina, stamina doesn't seem that important, and potions can give me stamina whenever I need it - but carry weight to haul loot is kind of nice.
Final question - can you poison both blades for tough enemies? I think you can only apply poison to your right-hand weapon, but if you switch hands, will it retain the poison, so that you can then poison the other weapon?