I mean, it's by far the least represented game, even more considering there's only two characters from Tactics while Tactics itself has tons of them (regardless if you count the Advance games or not).
Currently, we only have Ramza and Agrias as Tactics characters in Opera Omnia, and on top of that, they aren't that developed. Well, apparently, Ramza recently got a FR, which was all he was missing, Agrias is still missing both FR and BT (funny, considering that, at least on GL, she is commonly present in banners), but at the end of the day, Ramza only got both a BT and FR because he is the protagonist of Tactics. They've been handing FR and BT to "minor" characters, so to say, so Agrias could definitely already have gotten something of the sort. But anyway. It also took a lot of time for Ramza to get his FR, which just further shows the abandonment Square has given this realm.
And don't even get me started story-wise. It's already awful that Laguna basically stole what was Ramza's compass of light, leaving both Ramza and Agrias completely lost during Act 3. We don't even know where they are in Act 4; we lost them thanks to mister president, congratulations. And even before that, they didn't have a big impact story wise. They interacted mainly with the characters of FFXII, due to them also being from an Ivalice, and occasionally interacted with others. But it was also very scarce, you'd barely noticed them almost.
I sometimes wonder if this is intensional or Square just really has no idea of adding anyone from Tactics, at least not soon. I mean, they've added all Dawn Warriors, they've added Braska, they've added Nabaat, they've added a bunch of people that are far more shocking than adding Delita or Cid or Alma or others from Tactics and/or the Advance games.
This does leave me to wonder if Ramza and Agrias being "left behind" is an allusion to Tactics itself and how Ramza is a "lost hero", the true hero, but not the one that received the glories (those went to Delita, from what I understood. Orran was in charge of making sure Ramza's journey and accomplishments were written down, since no one would ever give an heretic credits for saving the world. And Orran isn't no one, so he'll do it ☺️). Still, it leaves me pretty hurt, because, although I haven't ever played Tactics, I watched its story and I really liked it. But if Square is just gonna forget about them, there's no chance Rapha will ever be added 😔 (she's my favorite character of the game, despite being opticional), considering more important characters aren't added either.
Honestly, it was quite the shock to me when I moved from RK to Opera Omnia, because in RK Tactics was a realm with lots of characters (not the most, I think, but close), so then being only met with 2 was kinda heartbreaking, tbh. It was also one my favorite realms to play around with, so you can understand the shock.