I've been trying to change the enemies that fight with Hojo in the first battle on the Sister Ray in Midgar from the Poodler and Bad Rap Samples into an Unknown 2 and Unknown 3. The enemy IDs, data from 0x0350-0x04bf, all attack related data have been swapped and the AI has been fixed, including pointers and Hojo's AI telling him to "kill" his monsters during the battle set-up. But they still won't appear; they are targetable, invisible, do not act and die after being the target of any attack (including things like "sense").
I suspect this may be something to do with their formation; when I change their formation to put them in the position in which they appear in the Gelnika, they appear in battle at the start but disappear when Hojo uses capsule on them (exactly the opposite of what one expects). When their position is the same as that of the Poodler and Bad Rap samples, the battle starts as usual with them invisible and untargetable, but they revert to the state mentioned above when capsule is used. I've remembered to put their IDs in the formation data every time
So after all that, what I'd like to know is what is known about formation data in the scene.bin (assuming this is the problem); there isn't any data on the wiki and a forum search reveals little of use. Or might the problem be something else entirely that may or may not require a facepalm for my ignorance?
Now for the (possible) discovery. I've noticed that the wiki says that the function of all the bytes from 0x00a to 0x0019 are unknown. They aren't. The first two bytes of this "unknown" data do something similar to
this field opcode. By changing 0x00a-0x00b from 5c03 to ffff I changed what happens when the player wins; now, when Hojo's first form is killed, there is a normal victory scene with Exp gained before the player is taken back to the cannon as if all the forms had been beaten. My apologies if this is old news, but if it's not, the function of those two bytes has now been discovered.