I did a little more research on Square's content when it comes to their characters appearing in other games. They follow a pattern so far, that I had not really realized until I looked into it some more.
First Cloud in Super Smash Brothers Wii U, he was a DLC character. Cloud came with, two costumes, a stage, two songs, Chocobo Mii outfit & a Geno Mii outfit.
Next is Noctis with the Assasins Creed festival, vs. the small appearance Final Fantasy 15 had in Assassins Creed Origins. In the Assassins Festival Ubisoft clearly gave away a lot, they gave costumes, hidden blade mechanics and even added a whole mission to Square. Then you go to Assassins Creed Origins and all you get is a small appearance by Ardyn and you get Noctis's Engine Blade. Its clear here that Ubisoft gave more to Square, than Square gave to Ubisoft.
Now onto Noctis in Tekken 7, surprisingly Noctis only comes with two songs. He comes with Apocalyptis Noctis and Stand your Ground. Much like in Cloud's situation Square again is being very stingy with their music. The only other content that Noctis came with is his stage and when you bowl in Tekken 7, Gladio Prompto and Ignis are cheering you on. No other character in Tekken when they bowl has other characters cheering them on, so that is a nice touch. We see here Square is using Tekken to promote Final Fantasy 15 and the fact they had DLC passes going on for FF15.
In Monster Hunter World, again Square only allowed to pieces of music in their crossover. Those songs are Kulu Ya Ku theme also known as the Chocobo theme, and Torn from the Heavens (Behemoth Battle Theme). In addition to two songs, Square also let Capcom have a Behemoth boss fight. And armor from Behemoth and Moogle armor. So in another unsurprising move, Square only gives the bare minimum when it comes to their music and their things. Also Square used Monster Hunter World to promote FF14 Heavensward expansion to Final Fantasy 14.
2B in Soul Calibur 6 is hard to say how much music she will come with as she hasn't been released. However if we follow Square's pattern its most likely she will only come with two music tracks. And again we see Square characters as always being DLC and not part of the main game.
Following all of this information we have been given we can sort of determine Square's guest character pattern. And how much content they will give in terms of future Square characters appearing in games that aren't owned or developed by Square.
1) Square only gives two pieces of music each time, when it comes to characters being in games that aren't theirs.
2) Square will give some of their content to the other game company, but very little.
3) Square will use this opportunity to promote their own games, by cross promoting
4) Square's characters are always DLC and they are not part of the main storyline of that game.
5) The characters from Square used in other games that are not owned by Square. Always represent the company, and are still relevant.