Is there any way they could add something to the sightstone to tell us how many of the maximum wards we can put down have already been put down? They tell us how many charges are left but they don't tell us how many we have put down already.

I believe there is already an indicator above your HUD that tells you how many ghost wards you have left before you need to refill. There was another discussion about the inherent difficulty of distinguishing between ghost wards, normal wards, and allies' ghost wards (as from another sightstone). If that is what you're commenting on, it would be better to dig that one up and post there.

This is actually easily solved by learning to utilize timers for everything anyways. at higher levels of play you need to know rough timers for important enemy ults, enemy flashes, buff spawn timers, dragon timer, baron timer, sightstone is just one more timer to keep track of.