I play support most of the time (Mostly because I hate the waiting time for a supp in queue), and I agree with you on the FACT that support items suck for the most part; and that the dependency on your ADC usually makes you fall off the second you are by yourself. However, I also have to agree with adding more AP to those items not being the solution.
I think that the support role needs to be diversified and strengthened, and since we can't directly change champion's stats because it might have terrible effects on other lanes, items would have to be the way to go.
To begin with, it sucks that as the support you are ALWAYS behind in gold and XP... always! Of course, if your AD is doing great, you will both be ahead of the enemy team... but you are always still behind your ADC (And just because you are the support and your job is to help/protect the adc, it shouldn't mean you always have to be sacrificing something for it... HELL you are already sacrificing EVERYTHING for it [it = ADC].
I think the gold income from support items needs to be increased, either by giving more gold, or giving the same gold but in shorter spurs of time. I have a support rue page where i run gold quints and all that, but at the cost of always being slightly weaker early levels and that SUCKS and it's unfair!
Maybe make a support specific summoner spell (i know exhaust is the go-to, but listen here....) that when chosen, just like smite, makes a certain item at the shop available for the champ running that summoner. Then, with that particular item, we could give supports better stats so they can be AT LEAST at the same level as their ADC.
Another problem with supports always falling behind, is also being left behind. While LoL is supposed to be a "Team Game" we all know that it is VERY rare when a team actually plays/behaves like one (unless you are a premade 5 person team ). So in my experience as support, unless I have a good friend being my ADC, as soon as i am able to get 3-4 kills under my ADC's wing, they tend to start getting cocky and doing more solo things around the map. Once they have 3 good items or so, they could not care less about what happens to the support, and as the support, since your items are all utility and suck, you spend a good deal of time running behind allies in order to get some fun out of late game.. else, you might be able to clear the weaker jungle camps while the damage dealers of your team eat up the enemy base at their own pace.
And it would have to be through Items, if they try to change the champ stats to try and help out, they will probably end up damaging great champs like they did with Zyra. She started as a mid mage, but because her stats (and CC and range) were really great, and her ability kit is extremely powerful) people started running her as support, so she got super nerfed... now she is hardly ever seen mid, and even as support...
I love her and main her, and play her as Mid/Supp/JG, and when I ask my friend why they don't play her they all say the same... " She is way too squishy/base health is awful, her plants are TOO EASY to destroy (always compared to Heimer turrets, not only the turret do more damage, and take longer to kill, they are also easier to place in terms of CDR and Mana spent), and that she has no mobility... her base movement speed is awful, and unless you land a good root, or slowing plant near the enemy... you'll be deforested. SO for the sake of those mid lane mages who are still decent supports, do NOT suggest that rito fix their stats.
I don't honestly know if I made any sense now that I read all I wrote, I am just ranting, I know.... but yeah. I agree that in order to be a useful team player, and also have fun playing late game as support, you have to be selfish and "Sacrifice" a couple of item slots and get whatever items you want because you deserve it! (Sorry not sorry I didn't get a mikael's and got a morello instead!)
Rant over
-RG