The items literally exist for the sole purpose of getting you off your feet and fulfill their purpose well in addition to finally being in a healthy state where they are neither overpowered or underpowered. That said, every time riot tries to compliment something, it typically results in someone finding a way to make said thing broken and then it gets ruined due to overnerfs, and riot has to start from square once again. "Leave well enough alone." is my stance on this.
Despite this I am interested in hearing your thoughts as to why the items should be complimented and what those items would be upgraded into. I would look toward corrupting potion as opposed to the doran's items, and turn it into an hp item with the same active instead of a consumable, give it some cdr with no resistances and only the active becomes stronger as you upgrade it: healing you for more and increasing the DoT damage per lvl and have it scale with your hp. I would say recover 5-10% of maximum hp and mana (per level) over time once the item is completed, and have it increase the damage of their next two spells by a percentage equal to their maximum hp, and have it do exclusively magic damage so that you can't stack it with titanic hydra which is a borderline broken item already. I feel this is a better idea as it is easier to tune tanks who can fall back on their other defensive items, whereas pure damage mid laners and adc's have only their damage to rely on and nothing else causing them to fall hard on their face; damage which has been buffed to insanity and for the marksman in particular.
The reason I put no resistances in there is because the tanks who build the most hp often have a shield that scales with it: Skarner's w, Nautilus' w, Malphite's passive, Vi's passive, or beef-tanks with damage that scales off their hp: Volibear's w bite and his hp regen, Sejuani's w, sustain tanks: Maokai's passive heal after he's cast enough spells Mundo's passive and his ult, Garen running away like a coward, or Gragas' passive whenever he casts something every 8 seconds. Those tanks all have a means of surviving and being useful based on their hp alone and benefit heavily from cdr due to being caster based champs so the resistances would make it a bit too overpowered and would bare too much resemblance to locket of the iron solari and spirit visage which provide hp, resistances, and an amount of hp regen, in addition to cdr. Taking away the resistances also prevents it from being abused by tanky mid lane mages like Swain, Malzahar, Anivia, Taliya who need the mana from RoA and cannot afford to divvy up their damage.
Anyway, I focused on tanks because I feel that they are in a nasty spot right now, and need some serious love thrown their way. Cinderhulk's utility is fine despite people's non-stop complaining about the hp nerf, and despite my personal dislike of the item in general, finding quill coat to be the superior jg tank item because it gave much needed defensive stats and didn't force you to take turret aggro from the immolation passive when trying to set up a play for someone.
With all that, I still think someone would find a way to abuse my item idea, but DoT is easy to build against because the damage comes in small ticks as, which makes it fair and not bursty as shit. It's one of those things you would have to be aware of during the fight, and if you forgot, well then it's your fault and not the item's fault for being broken. Not that riot will tell you something is your fault because they don't want to lose players.
