It's good that you're taking the time to really plan out your characters. A few times I've fallen into the trap of making a character that I thought would be awesome, but soon grow to dislike and abandon.

Your construct idea sounds good. Your keeper could work, too, although it's a bit unconventional... Having your expertise being to help other Keepers' creatures will make your guy weaker in other aspects. A more aggressive Keeper with no interest in making friends might try to take your dungeon rather than ally.

So yeah, keep tossing around ideas until you're ready to post. Getting a few pages behind shouldn't screw you over much, at least in the long run.