They should create a champion dependent on a "mana vamp" passive.

A passive that turns a % of dmg dealt with abilities into mana. The catch being the champ starts with an unusually low mana pool/mana regen and has really expensive mana costs to their abilities, while being cripplingly dependent on spell casting. Failure to deal the dmg with most of your casts mean running oom frequently in lane. While deal 100% of all dmg in each cast will result in typically having more mana throughout lane then most champions, of course allowing you to have more success on top of the amount you are already having. However as the game goes on, the champion gets a lot more mana to the point they have the highest base mana pool/regen.

Ramblings: The reason this idea comes to mind is because lately I have come obsessed with and paricularly with how it synergizes with . In particular I really like the combo of along with the rune "Presence of Mind". If you don't know off hand, Muramana turns 2% of *total mana into Attack Damage. At a cost of 3% of your mana 6% of *current mana is dealt as bonus physical damage, so as your mana lowers the bonus dmg will as well. So its best to keep your mana as high as you can at all times hence Essence Reaver and Presence of Mind. Essence Reaver effectively turns that 3% cost to auto in 2% by restoring 1% of your mana per auto attack. This makes Muramanas passive both more effective and more efficient with added benefits of more mana and ten seconds following your ult of 50% attack speed and 20% remaining cooldowns on basic abilities. Presence of Mind then restores 20% of missing mana and Removes 10% of your ults cool down per take down allowing you to benefit from Essence Reavers second passive more often making that item more effective and also making Muramanas passive yet more effective and efficient.

Further Ramblings: The sort of dream champion I have come to imagine is one like Riven or Lucian. One that casts a spell and autos, spell, auto... The spells empowering and facilitating the auto attacks. A difference being this champion doesnt burst, they are in it for the long drawn fight. This champion lands a spell to primarly refund the spells mana cost depending on the "mana vamp" and empower the auto with high %dmg life steal. Additional effects of the abilities would be bonus movement speed, attack speed, vision, slows, or ghosting while attacking targets the ability landed on(just an assortment of continuos auto attack facilitating effects). As for what this champion uniquely provides to the team, that would be entirely in their ult. It would cost 50% of total mana and scales off that amount. After a short delay they emit a powerful burst of magic that heals allies and for a couple seconds gives them a small sheild for couple seconds for the excess. Enemies that are hit take Magic damage and that applies to the "mana vamp". For a duration following this any dmg done by healed allies to any damaged enemies by this ult including the caster will "mana vamp" to resore the masive amount of mana it costed as much as possible. [sg-jinx]