Yeah, I have thought about this as well. However, it's not possible to implement with the current system: You can ping exactly one thing about an item, which is CD/"Ready" for most items, charges for wards and gold to completion for incomplete support items. I don't see a solution to that, it would mean that you can ping two different things for exactly 3 (or 6) items which is simply not worth the effort of coding. Also, how do you decide what to ping? There has to be a method of selecting what to ping, or you make the relic shield charges the primary thing to ping. Then you only flipped the issue on its head, because now you can not ping you are about to finish your quest. It's a really tricky situation after all.
My proposed solution is to make every effect on your champion pingable.
That's right, every single buff or debuff present on your champion. This would require some engineering work, but it ties in nicely with the current ping system as most of these are produced by items (most of which are already pingable) and champion skills (which you can ping the CD of, but not convey additional information).
That fixes the relic shield problem, as you can ping the gold effect to communicate how far you advanced your quest and the recharging effect to communicate the number of charges and the time to your next charge.
It also would be a huge improvement to the game itself, as you can communicate some things about your champion better. E.g. ping the recall effect to show you are recalling and your duo lane partner should too, ping the effects of 
and 
to show who you are connected to.
That would even improve some abilities you can not ping the status of currently.
I never played 
, but I imagine pinging "Passive: Ready" can be confusing, but if you could say "Demon shade: Demon form" that would be much better.
Finally, there are important effects generated by enemies. "Grievous Wounds" or "Slowed" or "Grounded" are important effects to communicate to your team, and there is currently no way of doing so.
So, my solution is probably a bit larger than you imagined, but I hope Riot can and will do this. It surely needs some coding to get it all running, and some work to determine what to ping for each effect (Name, duration, and source would be great, but some need special work, e.g. charges) but I do think that the advantages are well worth it.
Oof, that's a wall of text I wrote, I really hope a Rioter can see this and comment on it.
