I was a bit surprised that Final Fantasy's April Fools bit about romancing was indeed, an April Fools Joke. However, as stated by a community leader, there is a possibility that it may become a reality in the future. But, it's possible that the developers have hit a brick wall on how to actually implement the system in the first place. So, I have come up with a solution, hopefully THE solution that will allow the developers to implement the system(s) nicely.
First and foremost, to be able to "See" Romancing quests, there should be an unlocking quest given to the player(s). This quest should be given by a certain type of NPC, such as a Divinator, Fortuneteller, Wedding Planner, etc. The item can be either a headgear piece, or a ring. Both types would have a heart-shape somewhere in the item's design to let you know that it is for romancing/etc.
Second, the rewards offered. Similar to other reward systems like the hunt, Wolf Arena and Front-lines. The Romancing quests should offer not only affection toward you from that NPC, but an applicable amount of a special currency used to purchase special items. There would be two types of this currency, one would be a general affection-based currency, and one would be the harder, intimate/lust currency.
Third, Affection System itself. It would be quite hard to implement affection meters in the general world when talking to an NPC, so that's why the equips would be required to actually see these new UI Elements. Take a hint from Breath of Fire series though, and add on a jewel that changes colors on top of the NPC's dialog (via small talk.) This extra "Layer" of the dialog would only appear with the aforementioned equipment... equipped. The jewel would start out neutral gray / blue / aqua colored to indicate you're just another person and/or friend to them. As they grow to like/love you more, the jewel would slowly start to turn red, pink... and even the "lust" based Purple. Depending on the colors, you'd get different quests offered by that NPC (Daily I might add, similar to that of the Beast Tribes. But instead of the repeatable symbol on the quest icon, it'd be a heart symbol.) These quests could range from defeating specific mobs, getting certain crafted items, or very, very rare materials. (And in some cases, some may ask for certain currencies, such as allagan tomestones, alexandrites, etc.) Players should take note to be careful when playing with a woman's (Or man's!) Heart however. If the NPC tilts toward Lust/Purple, the quests may start getting stranger, as Lust isn't normal love or affection.
Fourth, NPC Dialog. As much as I'd like to see this system added as quick as possible, this is something extremely important. I noticed that the developers like to change dialog based on what you have done in the past/present. For instance, Hildibrand quest-line's Gerold will change his greeting in the quest-line if you did his quest in Camp Bronze Lake before meeting him in Hildibrand. So, certain NPCs would have to change their dialog to certain changes in affection, even if that change is with another NPC. For instance, gaining affection with Y'shtola may affect Thancred's Dialog.
Fifth, Integration with future content. With Personal Rooms (And more importantly, Personal Housing) on the way, one would beg the question... would an NPC heavily in the Purple (Even maxed in that direction) find a way into your room? Slip under the--No, it's too embarrassing! But seriously though, it would be a good idea if we could have them visit every now and then. Maybe give us a buff that lasts X Hours based on the NPC and their level of affection.
So far, this is all I have to offer, and I hope people take time to read and give their thoughts on this as well.