Idol
It’s no exaggeration to say that the already very strong Idol system will become even more powerful when it comes to season 6.5 when it receives indirect upgrades from Riot.
Another point that makes the Idol system so strong when combined with Irelia is that Gnar himself also possesses the Attack system.
Challenge
In fact, the Challenge effect itself is not too strong as it requires your champion to defeat the opponent to have high attack speed.
Therefore, it would be most reasonable if Riot Games reduced the damage of 2-3 gold Challenger units like Warwick, Quinn or Tryndamere.
Inventor
Despite continuous nerfs, the Inventor is still a very strong system, as evidenced by the fact that many of its variants are at the top of the Truth Arena meta.
Of course, such a strong squad will need to be nerfed.
Martin 
Samuel 
Eliana