Artillery Mage Item Idea

So, as must of you propably know, the mage item rework is coming somewhere around early next year. It is hopefully going to solve a lot of the problems that mages and assasins have in their itemization. Because of this i think its about time for me to share one of my ideas that has been in my mind for a while now. Its an item for artillery mages and (ap)champions with really long ranged abilities. It is beacuse i tought it would be cool if these kind of champions had a uniqe item for them. Lets see it:

-70AP -10% CDR -Unique Passive: If your spell hits a champion when you are more than 900 units away from them, it is going to deal bonus dmg to them. This dmg is encreased by every 100 units with a small amount, up to 1500 units.

The numbers could of course be changed, i just wanted to show the basic idea.(900 units might be too close, and no idea on the base dmg nor the ratio). Also im not sure if it would need cdr or not. I think this passive could also be given a charging mechanism, just like ludens, so you wouldnt be able to spam it. The first synergies are obviously the artillery mages. But it could be used on others with abilities that have the potential to dmg an enemy from a long range. (your ult bouncing far from you, or ppl walking away from your passive) (R) (E and maybe Q altough she might be too close when it hits) (Just like brand E bouncing away from you) (RRRRRR) (R) (R if its far away from you enough) (Q) (R if you are far away enough from the one who steps on your shroom) (Q) (Q if hes far away enough from the enemies in his posion) Aaand lastly it could get some use on some other champs as on off meta thing. , also AP (E) and (R) As you can see it would really have a lot of potential users, so i think theres defenetly room for it. But ofc let me hear your tought on it.