Keep DFG in the game. But give it -25% movespeed.

With the removal of DFG and eventual addition of another NLR item, Riot is going to add another item with 120AP. But this just means it'll be a must-buy for mages looking to stack AP, no matter what else it comes with.

Imagine DFG as it is. Huge assassination potential on anything with a shred of AP scaling. What if, along with that same 1-shot potential, it also reduced your movement speed by 25%? With lots of power should come some meaningful tradeoff. And being significantly slower would let enemies catch you during your assassination attempts.

Old Athene's was the strongest item in the game, in my opinion.To balance out limitless wave clearing and potential to stall the game for sometimes over an hour, if you get caught out by the enemy you should be easier to kill. Not harder (with the MR on Chalice items). So why not introduce old Athene's but with negative MR and Armor? Something like negative 20-30 MR and Armor would mean the enemy is rewarded for going through your spam of skills.

We all know Riot hates Spell Vamp. It makes bruisers unkillable if they're allowed to itemize it. It makes champions like Vladimir and Akali stupid. With easy healing should come tradeoffs. An item with 30% would be very, very appealing. But in the case it came with a passive like "-20% max HP", not everyone who wants spell vamp will be willing to build it.

With current items there is no tradeoff to buying the strongest item possible, which makes sense of course. But when late game rolls around everyone will have very similar builds. Why? Because there's no reason not to. There's no meaningful choice in not buying the biggest ball of stats possible.

With applicable negative stats an item wouldn't become a must-have because it now comes with power offsets.