Set up an automatic, reoccurring payment on your account using Mog Station. Then set it to be paid from your Crysta balance. Add Crysta using Ultimate Game Cards.

No, you won't get the time paid bonuses right off the bat, but you will get them as you accrue time in game and it's paid.

One caveat: The "add Crysta" options come in $10 increments, except for the $15 level. I discovered the other day that if you add $20 of Crysta from a $25 Ultimate Game card, you lose the remaining $5 balance. So it's best to get multiple $10 cards.