A Suggestion on Reducing Support Item Poaching
Presently, the aggressive support items (
Spellthief's Edge and 
Spectral Sickle) can be poached and exploited by laners for increased income without sufficient penalty. This is what allows a champion like Sona to operate outside of the support position so freely with as little wave-clear as she possesses, and what will likely ultimately allow champions like Soraka or other hard-scaling supports to thrive in top lane regardless of kit changes, while the lane is as grossly decayed as it is now. Top lane will require significant work in order to remedy, but reducing or removing the presence of support item poaching can be done sooner, and without negatively impacting support as a position.
In season 9, the placeholder solution to this problem was to make it so that your gold-generating mechanics for Spellthief's Edge and Ancient Coin would not operate unless you were near an ally, and this placeholder lasted far longer than the support position deserved to experience. According to Rioter Mark Yetter this change is slated to return in 10.5 for the aggressive items — but there were and still are frequent instances, in every game at every skill level, where you are simply not near an ally, but can still reasonably expend procs for the aggressive support items in order to zone opponents, and attempting to do so with the "leash" penalty felt more like you were being punished for doing your job effectively, as procs were consumed with no reward; fully reinstating this mechanic is not the answer, as it would simply be penalizing supports for the actions of other positions, which has been a recurring theme of support for multiple years now.
The present attempt at dissuading poaching is to make it so that minions give you increasingly reduced gold if you take more than 20 minions per 5 minutes — however, with a high enough CS per minute score, you still ultimately earn more gold via the support item and minions combined up until a later cut-off, than if you were simply last-hitting perfectly; and beyond that, you can elect to only occasionally take minions and focus on damaging your lane opponents for procs instead, in order to keep your minion gold intact, which will allow you to keep pace and eventually leap ahead of standard laning income.
My suggestion on how to cull support item poaching is an added penalty to proc and passive gold income in exploitative cases, alongside a partial leash mechanic, which comes off if your usage of the item is proven to be legitimate:
If 3+ of your first 6 procs were while outside 2000 units of an allied champion, proc gold is reduced to 7 and passive gold per 10 seconds is reduced to +1; this check is performed again every additional 6 procs. If the check is passed 3 times in a row (18 procs, at least 9 with an ally), the item continues to function as it does on live.
Additionally, if at least 60% of your overall procs were while outside 2000 units of an allied champion by the time you complete your first support item quest, or you have activated the reduced minion gold penalty (>20 CS per 5 minutes), proc gold is permanently reduced to 7 and passive gold per 10 seconds is reduced to +1, with the latter returning to +3 when the second quest is completed (i.e. the item is fully upgraded and procs are removed).
This is effectively the flip side of the current minion gold penalty — reducing income from both minions, and also procs, to make unintended use cases for expedited lane income much less viable. By causing both forms of income to be lowered to values beneath standard farming, the appeal for solo-laners drops substantially; and since the only method to circumvent both the recurring proximity checks and the 60% total proximity check outside of bot lane is to purposefully avoid expending procs until your jungler is nearby, or by consistently abandoning lane to roam without damaging your opponent, the effectiveness rapidly diminishes.
Even if you have a jungler essentially try to duo-lane with you for the first 3 minutes of minions in order to bypass this measure, that leaves your jungle free for invading, and the opposite side of the map at a significant disadvantage; and if you leave lane to get procs elsewhere, you'll be getting less gold than if you were simply laning. Furthermore, as the majority of champions that can abuse support items in solo lanes rely on AoE or multi-target abilities to clear waves, it's entirely feasible for lane opponents to actively sabotage attempts at holding procs by simply tanking the low-damage abilities, considering at early stages these champions have no realistic kill threat.
While this rule would still leave potential room for laners to use the support item freely up until the first quest completion, and then consider selling it off, the overall value of doing so is incredibly low, as the proc gold is cut early if you're not with a lane partner, thus keeping you on a low-stat starting item longer and longer; and for duo lanes, the reduced gold value for both minion kills and procs means they have no effective benefit.
The reach for this to splash over to actual supports is minimal — situations where you won't be with a lane partner for 9 of your initial 18 procs are incredibly rare, as are situations where you will be activating the minion penalty before the first quest completes; being able to manage your poke without taking minions (or while taking as few as possible) is a key skill to playing support, and opportunities to vacuum multiple full minion waves due to lane partner deaths that early on are hard to come by.
I had 45 minutes to kill and saw that the aggressive support items were being looked at for poaching again, and since I absolutely loathed the leash mechanic that was used in S9, with how often it ended up meaning you just lost gold (and at that time, damage) because you had to be somewhere by yourself for a bit, I wrote this up. The S9 leash did keep solo-laners from taking the items, but it also made the items feel much worse for actual supports, and defaulting back to it isn't necessary.
