Giving Thornmail the Last Whisper Treatment

I feel that Thornmail, like the old iteration of Last Whisper, is a relic that presents a problem: people who want more out of Thornmail want something able to act as more than just a theoretical anti-lifesteal component to themselves, but at the same time would giving tanks the ability to prevent themselves being killed by what in all honesty design-wise they are meant to be killed by (auto-attack based champions) be healthy for the game?

It is the same problem that Sterak's Gage sees in ADCs: the item as it currently is can be used by a class specifically to counter innately - that is, to act against in any theoretical given situation - their intended weakness, in a way that disrupts game health as it relates to assassins, and how do you let assassins deal with ADCs better without buffing them against other squishies?

So what I feel to answer both concerns would be to turn Thornmail into a new sort of Last Whisper: weakening the power of the item innately but then allowing it to build into multiple other items depending on the situation. Either Thornmail itself it would be weakened and then multiple item builds would be made out of it, or a new item that could build into Thornmail and alternative counterparts could be added.

One final build item might be an answer to the on-hit auto-attack jungler craze that has left balance a nightmare for the past few patches: an item that would alter the Thornmail passive to respond better to stacking on-hit effects, perhaps changing the amount of incoming damage reflected (currently 15% + 25% of your current bonus armor) to be impacted depending on how many on-hit effects are applied by a single auto-attack.

Another item build could be a means of incorporating anti-healing as Mortal Reminder does for those who upgrade Last Whisper, perhaps allowing such an item to inflict Grievous Wounds on a target auto-attacking the champion for four or more attacks for x number of seconds in a given period of time.

In both of the cases I mentioned, the items I mentioned are not meant to be all you need to defeat an enemy champion i.e. stand around and let the champion kill themselves attacking you. Instead, I think that Thornmail can grant champions who invest in it a means of answering certain situations that don't seem to have an answer, generally which can be seen in the late-game where the number of on-hit effects and self-healing can get pretty ridiculous and auto-attack champions reach their peak of prowess.

In addition, Thornmail's interaction with other armor items shouldn't rely innately on a simple number value, i.e. building an armor item for the sake of building an armor item for bonus armor to boost Thornmail's passive. With the proposed change, a shift away from the dependence of bonus armor damage value should be taken, and instead the upgrades serve themselves to better interact with other armor items.

Some armor items help to reduce the occurrence of auto-attacks in a given period (Frozen Heart, Randuin's Omen), or they promote getting and then sticking onto a target who is then forced to deal with you (Dead Man's Plate, Sunfire Cape). I hope that if this idea is taken to heart, the items would put less focus on stacking bonus armor for the sake of a bonus armor value, and more for what each armor item brings to the table.