Oh wait I just saw your name in another thread asing about just that. Answer is you might be able to add those entries via save editing but I don't know for sure. Your best bet would be to do another full runthrough from start to finish(not NG+) while using a game trainer or cheat engine to make things faster.

By the way doing that may mean you gotta do it across multiple playthroughs so you can get those scenes AND recruit them into Class 0

I doubt it. Mostly the kind of things I have seen in this community are either mods or memory editing. That's more of a flag hack which may be save editing or possibly could be done with modding(though that would be permanent until you do a clean install so not sure you would want that) If I remember correctly the rubicus is one of the things you keep when you do NG+ and you can do NG+ as many times as you like. If you are only missing the entries for just those NPCS then just do NG+ and run a basic runthrough of the game fulfilling the requirements for those characters to join class 0. That said don't forget to fail 1 of each of their quests to get the extra scene of them being sorry things aren't going so well. Once they are recruited all their quests become unavailable in the NG+ so those scenes are truly missable.

So far as I know 1 and 2 were released on Steam at one point but were pulled for some reason. I am also told all the mainstream games(aka 1 through to 15 including direct sequals such as 10-2 which is already released) are infact planned for steam release sooner or later. They released a few of them really close together over the past 2 years but have apparently slowed down cause all resources are being poured into the FF7 remake which has already been delayed a LOT and that's just for the PS4 release. Somehow I bet they will release it sometime near Kingdom hearts 3 which will cause both of them to bomb in sales and maybe delay further releases even further which SE will blame people not buying the game they just released(so close to another majorly hyped big name title) I personally have been waiting a long time for FF1 and 2 to make their way back to PC(hope they remaster or remake the PSP version not the GBA or earlier versions)and expect to wait a long time more.

That said cheat engine works on active memory so if you are working on that mod with that it may be difficult unless you know exactly how to go about it rather than modding the game itself.

I was just making a warning based on similar mods and hacks for other games I have seen. That said most of those were more save hacks rather than mods and they can work completely differently on such things so if it's a mod it might work better with less adverse effects and such problems as the one you stated may be possible to work around.

And forcing them open like that without triggering the flags for those roles could have any number of bad effects. I have seen tables to force things like this before in other games and they often cause either bugs or can even wreck the save completely.

No problems for me except the ones stated.

Doubtful. The crystarium goes up in stages based on where you are in the game. You can mod your save and/or emply a game trainer or cheat engine table to edit how many crystarium points you have and even mod your party's stats but the crystarium itself would be difficult I think.

hahahahahaha weirdest endings you say? Have you played 15 yet? lol Now THAT has a weird ending. Still you got good judgement in likeing 9. I probably took more of a liking to 8 cause it requires less grinding then 7 and the story keeps you going in larger portions rather than little nudges that 7 does throughout a larger world. Also there is the fact FF8 was the first game I got on my playstation.(course I got it when I got my first PS2 so I was late to the game)