Specific Item for Assassin Junglers

This is a concept I created with a friend. The item would read as something like: Passive: Gain X% (or a flat amount) movement speed while stealthed (includes FoW from bushes) Active: Enter stealth. This lasts until the champion deals damage or after 1 second. The first basic attack or single target spell in stealth deals X bonus magic damage.

The goal of this item is to give assassin junglers such as Kha'zix more ganking power in all stages of the game, as well as push junglers like Akali and Talon into viability.

Problems:

• Evelynn becomes terrifying with a permanent speed boost
• Currently has no build path
• Currently gives no offensive or defensive stats

Help and feedback would be greatly appreciated!