Is it possible to take the light armor path in smithing up to dragon, then go from Dragon and put a point in Daedric? So then you could make all of the light armors, dragon armor, and Daedric armor and weapons?

No, it's impossible. To take daedric you'll have to go the heavy side.

ok, thanks. If I'm goning to make an archer/assassin character, should I do the light armor path and buy the Daedric bow and arrows, or got the heavy armor side and make the bow and arrows and buy light armor?

I'd go heavy. Even without perks you can still improve your armor, only to lesser extent. The guilds will provide you with decent assassin gear so you probably won't even need to buy anything, and when you get to dragon smithing you'll be able to craft Dragonplate AND Dragonscale - so you get best weapons and best light armor in the game.
Also, I don't think you can buy daedric weapons. You need to craft or find them.

ok, and which dragon armor is the light armor?

Dragon Scale = light

Dragon Plate = heavy

Dragon armor can be improved to the greatest rating, and daedric weapons can be improved to the greatest damage output. If you want the best light armor, you can't have both unless you get all of the perks. I would go with the light armor and just improve glass weapons as much as you can, the difference isn't drastic and if you are a good assassin you won't need the best weapons to take down your opponents because you can get 30x damage multiplier on sneak attacks. Then again, you don't really need armor at all with assassin characters, you never really get hit, I didn't even wear armor most of the time and I play on master. I never leveled smithing up with my assassin, it's fairly unnecessary. Then again, the is the most aesthetically pleasing assassin armor in my opinion, and it is heavy armor, so you may as well just level heavy armor up and go for that because it looks as good as any light armor, has a muffle effect that makes it quiet, and then you can just put perks into one side of the tree.

I was planning on doing an archer with dragon scale set and daedric bow and arrows with plenty of perks in sneak, archery, alchemy, and light armor. Also enough perks in smithing to get me up into dragon.

In that case you either have to invest perks into all the smithing slots or not upgrade your daedric bow and arrows as much, which would make them weaker than fully upgraded glass. Once again, especially with a sneaky archer, armor is almost obsolete. I've played in cloth with such characters on master, your enemies never get to you. Here is my suggestion: level up the whole heavy side so that you can improve all of the bows up that side of the tree, including daedric, and then unlock dragon from the heavy side. That way you get dragon scale armor and daedric weapons with the minimum points expended. The sacrifice you'll have to make is having weaker light armor until you finish the tree, but like I said you rarely get hit and if you really want to you can level up smithing quite quickly. Just be warned that you may be underpowered in combat if you gain a bunch of levels from improving smithing rather than combat skills.

ok guys thanks for the help.