Custom rework: Tear of the Goddess upgrades
With Ezreal players claiming the nerfs to the champion are a step in the wrong direction, and that builds getting both Tear of the Goddess' upgrades should instead be nerfed, I would like to discuss the Tear items. The most common suggestion is to make the Awe passives truely unique, so that getting both items is hardly worth it.
I myself am really saddened and fearfull that this is what it will eventually boil down to now that a nerf to 'Double Tear' has been announched. I think that the build choice itself is worth preserving. They are both scaling items. Items which potential are not instantly unlocked once the purchase price has been paid. They trade early power for lategame power. If a champion were to purchase both and get both fully stacked, that should be rewarded.
Ezreal sort of cheats the downsides of stacking, not one but two Tear of the Goddess upgrades due to his inherent safety in his kit. But that isn't everything. He is also the only champion who really builds Manamune anyways. The primairy reason for this I guess is that Muramana's passive - Shock is really limiting the amount of champion synergies, and Ezreal is basically the only one that fits the bill. Additionally, Ezreal's kit inherent lacking synergy for critical strike forces him to find other items to increase his damage.
There are other champions that could really use the stats provided by Manamune, such as Kog'Maw and Varus. And maybe if the item was good, other champions not really needing that much mana might consider picking it up. Archangel's Staff as an example. A lot of the champions building it don't want that much mana, but the item as a whole provides enough usefull stats and is universally synergetic that they pick it up.
So I would like to make an attempt at the AD upgrade better.
Manamune

Recipe:
+
+ 
Stats: +35 attack damage +250 mana
Unique passive: +10% cooldown reduction
Unique passive: Awe Grants bonus attack damage equal to 2% maximum mana. Refunds 15% of mana spent.
Unique passive: Mana charge
Grants a charge every 4 seconds, up to 3 charges. Each basic attack or mana expenditure consumes a charge and grants +5 mana +8 mana, up to a maximum of 750 mana.
Total gold cost: I don't know, whatever would come out of balance changes.
Transforms into Muramana at full stacks. If Archangel's Staff is also in one's inventory, the first item bought out of the two upgrades takes priority. The other item will be left with 0 Mana Charge.
Muramana

Similairy gains an additional 10 attack damage and 10% cooldown reduction. Also like the AP variant, the transformation would increase the Awe conversion, to a final 2.5% maximum mana as bonus attack damage. Additionally I would change the upgrade's offensive and user-pool limiting passive to a more universally useful one.
Unique Active: Shock Mana shield
Drains 15% of your current mana. For the next two seconds, gain 90% tenacity for the first (15% current mana + 150) damage you take (shield damage included) (120 second cooldown).
If you also own Seraph's Embrace, both actives apply together, effectively granting 90% tenacity while the shield holds.
Additionally, I would make one final nerf to Archangel's Staff (and Seraph's Embrace) to make both items more equal, by lowering its mana refund to 15% from 25%, and lowering its cooldown reduction to 10% granted by Haste from 10% + 10% granted by Haste.
With these changes, I removed the single target/auto attack dependancy for champions to fully utilise Muramana. Additionally, I changed the offensive Shock passive to a defensive Mana shield active. This way Manamune users don't get a massive power spike on completion, and rather the Awe passive will grant more usefull attack damage when Muramana is finally obtained. Compared to it's sister item, Manamune nows stacks equally fast and requires an equal input of mana to gain stacks. Slower but manaless stacking just is not worth it.
Offcourse these changes would not take away from the fact that Manamune has no real other mana + attack damage (or attack speed) items to really scale with, but I hope this would be a step in the right direction. Anyways this is my attempt, take it lightly. Any numbers can balanced out, it's the thought proces that matters most.