Well, thank you again for your help ! It looks like I am mostly done. I have a few issues, though.
If I create a Druid5/Planar Shepherd 6, I already see 3 charges of Planar Bubble available, when I should only see 1, and then 3 at Planar Shepherd 10. I have the same issue with Plane Shift (I see 2 charges when I shoud see only 1). Do you have any idée why that could be ? In the mouseover-thingy of the Planar Shepherd class, the specials of lvl 7 and over are grayed out, so I don't really understand what happens here.
EDIT : also Plane Shift does not show up in the In-Play tab, even though I checked the "Show in Tracked Ressources List" thing.
EDIT 2 :Could there be an issue where the editor does not compile right when there are tags that are similar except for a single digit at the end ? I notice I have "issues" when I have tags like cPlSPlaBub and cPlsPlaBub3.
EDIT 3 : Here is an image ilustrating my issues :