Level 25 Bonus Idea

I like the idea, it would certainly make semi-carries and supports scale better.

But you can't have too big a bonus or imba things would happen.

Maybe things like:
Laguna Blade now purges (without the slow)
Time Lock now does double damage outside of Chronosphere
Lunar Blessing now scales with Luna's agility
Reduces Desolate search range

Small things like that which just make the Hero that much better.

I really like the idea of buying a 7th slot though.

Echo Slam now becomes GLOBAL, but bounces only occur if enemies are 500 radius near to each other.

Relocate now lets Io choose when to go back, but once 30 seconds passes, he will go back automatically.

Omnislash now doesn't stop until there are no more enemies in an area. Aghanim's Scepter adds the folling effect: Juggernaut gains +25 health regen during the slash, so if the slash were long he can regen alot of health but if it is short he can only regen a little.

Queen of Pain gains a new skill called 'Destiny Bond'. Targetted to enemy heroes, Queen of Pain commits suicide and kills the enemy hero, pierces spell immunity. Queen of Pain and both the enemy hero will have respawn time added 60 seconds and buyback cost x 1.5 (Extremely useful in Level 25 late games :P) Cast Range: 1

Earth Splitter will go to the end of the map, during the earth cracking, enemies will be drawn closer and closer to the crack with a radius of 525, they cannot Blink nor Force Staff out, but the drawing is not pierced to spell immunity.

Permanent Borrowed Time but healing will become damage hehehehe.

Spell Steal can steal 2 skills at a time, if steal more, the oldest will disappear.

Winter's Curse now effects whole map. Enemies temporarily gains unobstructed movement to walk towards the target Winter Wyvern selected.

Tempest Double becomes Tempest Triple, permanent illusions but if you cast the spell one more time the old ones disappear if they didn't die yet.

Dark Rift can now be cast on anywhere of the map, and all friendly heroes will be transported.

Some of them is only a joke :P