A few ideas, not all at once obviously:
Greevil's Greed bonus gold nerfed considerably, but all gold gained by Alchemist is now reliable (baseline passive, like Silencer's INT steal.) Also lowers the bounty for killing Alch by 15/20/25/30%, and reduce the cost and cooldown on buyback by 20/30/40/50%.
Acid Spray now applies to targets in the initial cast area as well as persisting on the ground. In addition to its current effect, units affected by the spray's initial impact have a 20% chance to be disarmed when they attack. Goes through, but is removable by, magic immunity.
While under the effect of Chemical Rage, Alchemist cannot die. If Alchemist's health reaches 0, his movement and attack speed are slowed by 50% and consumable items (and BoTs) are disabled until his health reaches 300/450/600 or Unstable Concoction ends.
Instead of dying upon reaching zero health, when Alchemist's ogre dies Razzil is thrown from the ogre in a direction away from his ogre's killer in a 30° cone 800-1200 units away. Upon landing, Razzil is stunned for 4 seconds and cannot use items. Razzil has 115 HP, -2 armor, and 240 move speed. He has 3 abilities: Unstable Concoction (which he can use to suicide or stun an enemy hero), an invisibility potion (breaks on movement), and a potion of control which allows him to turn any non-hero unit into a new orge. Due to his small stature, Razzil can freely path through trees. Razzil gains no experience without his ogre because Razzil is already an expert alchemist, it's his stupid ogre that needs training.
Being the ever-resourceful alchemist he is, Razzil can extract the essence of neutral creeps to permanently augment his ogre. New extra ability, 180s cooldown, bonus granted depends on unit consumed. General idea would be similar to Doom's devour, but adding base stats, armor, or attack speed based on unit transmuted.