Assumption:
Smartcast is an amazing function. Most champions benefit greatly from using smartcast on at least one of their abilities. Also, many champions benefit from having normal targeting on one or more skills.

Problem:
To enable smartcast for a specific skill you need to enter the key bindings menu and manually rebind the key for that skill. This persists into the next game where you will need to undo it if you should not want it there as well. All in all it's an unneeded hazzle.

Suggested solution:
Right clicking on an ability icon (or even better: CTRL+Rightclicking) enables smartcast for that skill for the remainder of the game. It can be toggled off again the same way. The status of smartcast would be shown by a coloured border, a little S in the corner or something similar.

Result:
You'll be able to change your smartcast settings on the fly without being forced into several sub-menus. This would also allow you to clealy see what abilities has smartcast toggled on, as opposed to now where you have to remember if you enabled smartcast for your Q in that last game, or manually enter the menu to check.

Possible drawbacks:
- If the option to enable it is too simple (say; just an ordinary rightclick) people may activate it accidentally and be confused. This can be solved easily by making the activation require an additional keypress (as in: CTRL-Rightclick)

- The interface may not currently be set up to be able to handle this, causing such a simple change to require quite a bit of work. This one I can only speculate about unless someone from RIOT feels like elaborating.

Conclusion:
This would remove an unneeded inconvenience and might even introduce the smart-casting system to more players due to better accessibility. It is also likely to be a pretty simple change (see above for why it's only "likely").

Any chance of seeing something like this implemented, RIOT?

I can't think of any champions for whom smartcast isn't amazing - once you get used to it - (though there are still about a dozen or so champs I haven't played yet) but I definitely agree with the OP; the option should be there, it should be a simple toggle, and it should be spell/item specific. I personally prefer the border idea.

This is a great idea. Many champs have a skill or two that would benefit greatly from this.

You have champ skills that smartcast perfectly; like fire-and-forget offensive magic and single target support spells. Then you have the skillshot and AoE spells that are improved by having the extra step of seeing just exactly where they're aimed and how big an area they while affect.

The main problem I have now is that these skills are not normalized across champs: having one champ with an aoe ulti (R) and another with aoe on W or E. And still others with skillshots on Q. Switching champs makes remapping a virtual nightmare as stated in Squirry's original post.

This isn't really an issue with well used champs, because of course we learn the where's and how far's. It's just this was pushed to the front by the arrival of Xerath to the Field of Judgement. He brought with him a skilshot, with two different ranges, and an aoe. Smartcasting with him was a challenge at first especially the locus/unlocus arcanopulse.

I was just thinking the same idea and was going to make a new thread. Smartcast toggle!!!!! Need some riot feedback in this here thread!

You could do what I do and bind smart cast q to shift-q, etc, then makes Caps lock your vent push to talk key.