This was discussed, very briefly, in a live letter awhile back. Here's the quote.

Q10: In a previous interview, you mentioned that we will able to tackle instanced dungeons by ourselves. Are there still plans to implement this feature?

A10: Yes, there are still plans to implement this feature. While there isn’t too much we can reveal at this time, just to give you a preview, we are currently discussing a new type of content where you will control your own unit for your grand company, add NPCs in your unit, and take them to dungeons to level them up.
Haven't heard anything since though. I thought it was a cool idea, depending on how it was implemented.