Also don't forget that his relationship with Kitai is probably considered illegal. Since he is now able to furycraft, and I am sure he will be made a "Citizen", he is required by law to marry another Aleran furycrafter to produce strong crafters.
I don't remember off-hand if it was specified in the books that it had to be an
Aleran Furycrafter, just a Furycrafter. This likely due to the fact that it is assumed that only Alerans can Furycraft, the Marat 'savages' are just weird beast-lovers and the Cane are animals with strange powers that don't seem to have anything to do with Furies (I would think that's the general outlook on the other races and their unique abilities). Don't forget that at the end of Cursor's Fury, Tavi wasn't the only one able to put out the furylamp so easily, having never done it before.

If the law is that an Aleran must marry one who is of near-equivalent furycrafting capability, I would assume that Kitai will likely be of equal if not slightly less capability with controlling/manipulating furies as Tavi. Remember that Tavi's bond with Kitai makes them share similar traits (Kitai's eyes and Tavi's ability to resist sleep longer even though he showed no ability to metalcraft, his slightly heightened senses and some others I believe). Kitai is at a disadvantage insofar as Tavi is intrinsically familiar with the mechanics and theory of Furycrafting, as well as having been raised in a society of furycrafters, whereas she has only recently been exposed to it herself.
If the law was worded with the inaccurate assumption that it was
impossible for a non-Aleran to Furycraft, then Tavi has his loophole, which I have no doubt he would be willing to exploit if and/or when he and Kitai feel they are ready to publicly reveal their relationship (Aleran style marriage of some kind, as to the Marat they would need only to Mate, not make out/make love as they have done so far, to be wedded/mates). Granted, I would think this would cause an immediate hostile reaction from a majority of Alerans throughout the realm, regardless of when this would occur, but I wonder if even should the law be re-written, would the High Lords or Gaius himself be able to undo the legal binding of Kitai and Tavi should they be joined?
Regardless of how it plays out, either it will be a major issue in and of itself should it not turn out that Kitai will hold equal or near equal potential, or if they do and get together, then it will be an issue that is either a problem in and of itself, or that in having solved will create new problems as a result of the hide-bound and prejudiced Alerans.