How about a utility buff to wards by adding something to their placement radius when using them:
And that's "Line of Sight" highlight, where the radius the ward can actually give vision to is highlighted.
So it's not a buff to wards, but rather something to make their use a little easier.
EDIT: Adding a visual aid courtesy of my legendary paint skills.
https://i.imgur.com/aLVKPaV.png
Black Circle = Ward Vision Radius on indicator Blue Circle = Ward itself Solid Red shape = Terrain Green Outline = Brush Grey Outline = what would be highlighted in the indicator for what ward will grant vision of in the radius
The circle on the left represents ward indicators as we have them. On the right you see a grey outline to (roughly) indicate what would be highlighted in the new indicator to help people see if line of sight is a problem or not.
's active has a radius which is the amount of vision revealed. If this item had it wards can very easily have it. The only reason they don't is because Rito lazy.