On supports: Why not have wards last indefinitely?

I play League, and I play DotA 2. I main supports in both. The difference between them is, of course, rather large, the main one, it seems to me, being that supports in DotA are useful as gankers. Because disables tend to last much longer in DotA then in League, supports, even those who don't have nukes (though that's rare), can make some excellent plays in the laning phase. Other such discrepancies have been noted, such as the difference in the meta, and these sorts of things have led Riot to asking what they can do to make supports more varied, more interesting, and less of just being a ward buyer.

Much of what has been suggested has to do with runes and masteries. I dislike that solution for two reasons: One, it forces supports to have specific runes or masteries, and those who don't have them, whether because they are lower leveled (lest we forget that everyone has to start at level one with none of these helpful elements), have a clear disadvantage, and what runes to get or what masteries to put points into no longer becomes a choice, but a calculation (see relevant Extra Credits episode, http://www.penny-arcade.com/patv/episode/choice-and-conflict); two, it doesn't change the in-game experience significantly, as supports would still have to spend much of their time out of lane, warding, counter-warding, et cetera, rather than gaining experience or actually playing with their adc/marksman.

It is inevitable that supports are primarily going to be the ones warding unless Riot makes extraordinary changes. If supports are going to be allowed to make more choices, rather than being forced to spend all their time warding, the following changes should be made: make green wards last an indefinite amount of time without significantly raising the cost; make pink wards last an indefinite amount of time, but give no vision, only true sight (v. Dota 2 sentry wards), without significantly raising the cost; keep sightstones running under the same principle, i.e., can play 2 or 3 wards at a time, and they will last indefinitely. I imagine several things will result from this:

1. Supports will spend less time warding and less money on green wards.
2. Ward wars will be more significant and require more of an investment.
3. The decision between green and pink wards will no longer be one of being able to afford the clearly better ward, but rather an actual choice of what the team needs more.
4. Other lanes would be encouraged to buy wards, and it would add a level of conflict not currently seen.
5. Ganks would no longer be as easy. The jungler or whoever else is attempting to gank would have to be more creative or smarter about when they attempt the gank.
6. If ganks are no longer so large an issue, flash may be less required, and, again, the decision of what summoner spells to get may become more of a choice than it currently is.

Perhaps this has been suggested before; perhaps it has even been tried before. I don't know the history of League as well as I should. I think that this solution solves many of the problems that were brought up in the forum post, http://forums.euw.leagueoflegends.com/board/showthread.php?t=1375259. Thoughts?