many people complain about destruction magic being too weak.

Solution- every 5 destruction skill levels-
novice spells deal 1 point extra damage
aprentice spells deal 2 points extra damage
adept spells deal 3 points extra damage
expert spells deal 4 points extra damage
master spells deal 5 points extra damage

is this a good idea.

or change mana consumption reduction enchantments into a damage increase, that way, mana resource would not be a total junk stat.

Personally, I think it needs a lot more work than just a simple tweek.

But, to keep it simple for a patch/DLC. I think the best way would be to make it level similar to normal weapons. Every time the players levels in destruction, the damage output increases. And add the ability to enchant things that will increase destruction damage.

have you read my op.
i said every 5 levels of destruction, spell damage could increase.

Yes, I did. But why can't it level every time Destruction does?
Normal weapons do and you can still further increase their damage output through smithing and enchanting.
This is why I said for it to level every time and for enchanting to include a damage modifier.

You dont need to fix destruction magic solely, the magic system itself needs some tweeks and I really dont care if I have to pay for it in another dlc. Your solution wont fix it, it just make destruction magic a small amount of time more useful until it is outclassed again by raw melee/ranged combat damage.

To make every magic more useful you have to tweak some things in general:
- Better synergy effects for magic like for normal damage (enchanting: % power for magic school X spells, e.g. that would boost time and power of summons, dmg of destruction, healing, etc.)
- "magic smithing" improvements or new perks, instead of increase armor rating, maybe give something useful for mages
- Make magicka more useful in comparison to health. The way it is now you dont need any points in magicka if you use two schools, you barely need some for more then three because of cost reducing enchantments. So spend points in magicka is a waste, why not add something like a weak manashield
- Again better synergy. For example melee dmg enchants for weapons benefit from a) magic cost reduction, render soul stone recharging useless, improve dmg even further with e.g. destruction perks. Why not add some enchantment for staffs and co. that improve some magic attributes like magicka, magicka regen, +% power for magic school x

And another thing:
- Add more outdoor content or "large" dungeons like most dwemer ruins where followers like atronarchs can freely follow you without problems

normal weapon damage increases every few levels.

i like your idea but i still would like destrucion damage to increase every 5 levels.

Dual cast thunderbolt does 200 damage. And you can cast it pretty quickly. The DPS is higher than all but the super smithed(700 dmg) bows. It doesn't get the sneak attack bonus, but you can fire while moving where bows slow you down. Plus it knocks the enemy back. The problem isn't just damage. The problem is that spell cost two boatloads of magicka. With 0 cost spells its overpowering to the point of making the game boring. However anything under 75% reduction leaves you out of magicka in a few casts. Most enemies at level 50 will go down in 2-5 hits. So using your system it would do 400 damage. I actually like destruction, its the only combat skill that doesn't spiral out of control if you max out everything. 200dmg for a fast attacking ranged spell is fine, especially with stagger.