I would love to have an AD version of spellthief. 
but +2 AD, 
but +8 AD. 
but +25 AD and a related passive. Just as we're seeing Zyra and other mage supports, an AD Spellthief line would enable some AD caster support options.
Automatis3 votesHell yeah give me some support for my favorite supports 
RookPusher2 votesAt the risk of sounding like an idiot, who's an AD caster support?
Aptest2 voteshonestly I'd love to get an AD item on Bard, Sona, Blitzcrank and a host of off-meta supports.
How come ADCs get to have a gold AD item, and supports do not?
no justice.
Mylon1 votesDid you know Thresh E scales off AD?
Support Varus is surprisingly strong. Like old support Nidalee but with an easier to hit nuke, waveclear, healing reduction, tank shredding, and a root.
Support Jhin gets roots, traps for vision/zoning, very strong poke with passive, and he has retarded base damage on his ult. Plus his passive turns stats into AD which boosts the scaling of his spells.
Support Yas has good poke, burst, and an improved version of Braum wall.
Support Yorick has good poke and can create a 3v2 at level 6.
Support Urgot has Armor shred, slow, and good poke/zoning.
Sona Ping1 votesNo, you are fine to ask that, as it's not surprising that a person be a bit confused. And that's because the answer is that there really aren't any.
RogueWill1 votesAt the risk of sounding like an idiot, who's an AD caster support?
are pretty decent AD caster supports
The Minion hunt1 votes
can do it, but your adc gotta play safe when not mega, and he scales of everything.
Cubíx1 votesThe biggest problem with this idea is there really isn't alot of AD supports, I mean a few off meta choices but thats about it.
IcyPepper1 votesNo.
There's a reason why Riot doesn't support AD supports, their builds, or even making them in the first place. It's a balancing nightmare, similar to how some AD bruisers with cc are more difficult to balance and overbearing when the meta favors them (Vi, as much as I love her, is an example why you shouldn't give AD bruisers too much cc).
Linna Excel1 votesNot enough AD supports right now to justify it.
The Minion hunt1 voteshave you ever seen a utility ability scale of ad? support bring utility to the team, heals, cc, shields. I don't think riot should be assisting in troll support picks (just my opinion).
Mylon1 votesBecause Annie support's utility totally scales off AP.
The Minion hunt1 votesAnnie has one stun. She is a early game support. Eventually she needs gold and if not fed that ult wont do much to a front line.
ShinkoMinori1 votesTry Jarvan Support. I saw it once rek the bot lane.
Milodic Mellodi1 votesPretty certain you only really want the Active, and the thing is we all know it'll never happen. Because when it comes down to it, a Zed getting increased damage while being able to catch up to an enemy makes for a fed Zed. Jhin would conquer lane because once he builds it he can just use the Active and deal increased damage (with the added AD from the item).
Marksmen, especially those that can dash like 
and 
, would abuse the slow; and the thing about Marksmen is that they can either deal low/medium damage over a lot of attacks, or a lot of damage with less attacks, and the additional AD with the slow just seals their lane. It's probably end up being an Early Game staple for most AD builds.