What Issues Are Being Targeted In The ADC/Marksmen Pass?

So we all know that marksmen are going to receive a pass similar to that done for AP items and the Juggernauts. But what else is motivating the pass (if those kinds of general thoughts can be divulged before the specific details announcement is brought forth)?

More specifically: My issue with ADCs is that they can get locked down and blown up, but building defensively for those situations outside of item# 5 or 6 puts you so far behind in sustained dps. Going straight for their damage dealers isn't always possible because of their front line homing in on you to lock you down or tearing you apart; staying behind to safely hit them while preventing their damage from wreaking havoc requires a lot of coordination with the allies, which in soloQ is just not possible or reasonable to attempt apart from your own gameplay.

And of course, the item pathway is so stale. In general, rush IE -> Greaves -> PD -> any combo of LW/BT/BorK -> either GA, BT, or Merc Scim -> Zephyr if the games even lasts that long. More defensive items that allow Marksmen to remain in game without rendering them unkillable or being used as snowball items for damage outside of their intended use (e.g Bloodthirster as second or third item for more burst instead of as a defensive item).