Have forced in, people with set materia. But, they will all start at their correct levels. So you could train them up, if needed. Like the normal game, you could just level until your guys were OP, but, that would be boring. Like the original, is funner and quicker to just be tactful lower level, but, still lets you train-up if you ever need to get stronger.
As for classes, and enemies, I need ideas. But I have got the following. The aim -- is to make it as good as possible !
I will depict some e.g. classes and materia combos:
Mage (usually used for high damage spells in MMOs, but low health) - HP <-> MP (so from the off they can cast a bunch of spells, but will have minimal health); assorted attack spells/materia/
Tank - Cover; HP Up; (and then things to up attack some-what, if tanks usually have good attack, too)
Rogue/Scout/ - Speed Plus; Steal; Added-Effect & Poison; maybe a weak physical attack but 4 x attack
Healer - Usual Healer spells
Summoner - Similar to Mage, but with Summon Spells
Other
The idea will be... having a Healer may seem a good idea. However, due to how, perhaps, quickly you could defeat a foe with mainly attackers, it may be quicker to use them instead. It could be that a Healer has maybe weak Heal spells only. Or it could even be that you can select these ''combos'' of materia, meaning you have choose to have e.g. two Tanks and one Healer etc.
I have seen mods before where there are ''classes'' -- but I want to make use of more simple, already existing materias -- with a class system simple and like FF9 etc.
IDK if it should keep things challenging by needing to level-up
Or, if perhaps some materia could or should be modded to keep them from leveling up
IDK as well if enemies should all be made harder, as well as bosses, without changing the game too much -- so that battles will be challenging and enjoyable
Let me know thoughts, thanks