Vaal Cultivation Orbs in 0.4

I'm really excited for the new Cultivation Orb possibilities that are coming in 0.4.

It's my understanding that the Cultivation Orb removes up to 2 Modifiers of a corrupted Vaal Item (for example Atziri's Rule Reflecting Staff). Let's say it removes Intelligence. Than you get a new Modifier from another Unique Staff. This one doesn't need to be a Vaal Unique, does it? How do i know from which Pool the new Mod is chosen? And would it be possible that i get a Mod from another Staff that is already on my Atziri's Rule. I'm imagining something like an additional Cast Speed Mod (for example from Taryn's Shiver Gelid Staff).

I'm not sure if I got the Cultviation Orb right. Is there anything like that in PoE1? What do you guys think? Is it just a gimmick or will it be actually useful?