Not sure if its intended to work as an alternative, in which case CDs preorder bonus item already became "outdated", but the Loyal Zelniak Companion shares cast/cooldown/etc. with the Jann Magi illusion from CD preorder. Cant cast both, and the Zelniaks flavor text is even a complete copy-paste of the Jann Magi illusion flavor text...
The flavor text is a bug, it is different than the last pre-order bonus. They are looking into a fix now, the not being able to stack is intentional.
I think the main problem with losing the Jann Magi illusion when using the new companion is that you lose the floating ability and safe fall from the illusion. Perhaps this could be kept somehow?
Jann Magi safe fall/glide was a major benefit for Chaos Descending. The jury is still out on whether it will be necessary for missions, PQs, or other mobs in Blood of Luclin.