It's very easy now to get the most powerful armor by smithing and improve it to be twice better.

It would be better if you would first need to find the armor or weapon and break it up like in enchanting to be able to make the armor or weapons yourself.
You would only need to break up one armor piece and one type of weapon, to unlock all the weapons and armors of the same set.

Here's daedric armor and weapons example:

Get 90 smithing and daedric perk
Find daedric weapon, for example sword
break it up to learn how to create all the daedric weapons
Find daedric piece of armor like boots
break it up to and learn how to create whole daedric armor set

Then to improve your weapons and armors you would need to find books, you would need to go to some well guarded dungeons and find books which would tell you how to improve different armors and weapons,

There would be different book for each type of armor and weapons
For weak armors like iron, leather, steel you wouldn't need any books.
But for stronger ones like dwarven or elven you would need to find books.

Then smithing wouldn't be so overpowered.

What do you think? Is it a good idea?

Maybe a bit too much of a nerf, but I like your thinking.

It also would be more realistic than now, because no one magically can learn how to make a daedric armor from making iron daggers.

You would need to break up the armor to find out how it's made and read some books to find its weak points and how to improve them

No I've got a better idea - don't abuse it. Or, see sig.

I've suggested the same idea in my own thread (below)

It was met with some backlash, which I can somewhat agree with.

Personally the best route for smithing for me would be something similar, except make it so you can find any weapon/armor type at any point in the game, just extremely hard to find the more powerful stuff when you are lower level. In addition, make it so you can "craft" any type of weapon or armor anytime as long as you find one piece of that armor first. I.E. as soon as you get a dwarven sword, you can "deconstruct" it to create dwarven equipment, but if your skill isn't high enough, you'll have a chance of failure (to the point where if you even attempt daedric smithing at level 50 smithing skill, you will always fail).

The perks instead would be rebalanced to provide cool and interesting bonuses to your weapons or armor when you smith, or improve them. Stuff like "Arcane Smithing" perk is good, and maybe a perk that lets you improve weapons/armors to be lighter in addition to stronger, etc.