I haven’t played OG 2nd on Ex-Hard yet but as far as normal mode is concerned the only difficulty I had was from the language barrier and a few SR points. At no point in the game did I actually feel like the enemies were threatening. Annoying? Yes, but never powerful enough to give me the vibe that they could wipe me out. I think this is because the enemies you fight had lack luster damage output throughout the game. I wouldn’t want OG3rd to be like OG2 on the gameboy were armor was useless and even the super robots turned into reals by the end of the game, but in OG 2nd the enemies and bosses felt like the never kept up with your progression. On the other hand, like what they tried to do with giving the enemies the ability to inflict status effects on your mechs but they never seemed to be a hindrance to me all that much aside from the really bad status effects that paralyze your unit or remove the ability to use SP.
In OG 3rd I’d like to see them buff the enemies up a bit, make them feel dangerous. Maybe make the bosses use senshi’s more often or give them attacks that ignore certain senshi’s you have like invincible.
"Oh, come on. The worst that could happen is we all die!" ~Colonel Jade Curtiss, Third Division Malkuth Military (Tales of the Abyss)
I don't really think the games need to be easier or harder. I think more player control over difficulty would be nice. Remember in J and W where you could make the enemies more upgraded as you beat the game? It didn't make the game that much harder since enemies weren't more accurate. Nowadays, it WOULD make the enemies more accurate.
Z2 had this thing where you couldn't drop some enemies below 100 will. It diminished the usefulness of Daunt, but at the same time, kept the enemy from losing a quarter of their armor. The thing about status-blocking is that you can't give it too many enemies, or else status attacks become completely-useless if you decide that Fury can't go through. On a last boss, that's understandable. Maybe even on weirdo extradimensional or alien things.
Map attacks that block spirits would increase challenge. As long as there was a way you could get around it. Now, if that was the boss' schtick, that you had to defeat it with the possibility of not using spirits, that's fine, but if an ability or attack is given to too many enemies it cheapens it. They could stand to get creative with map attack AoE again.
Y'know how Toutetsuoh and Kyuukioh had that ability that reduced will for all units in range at the beginning of the turn? Make some more abilities like that, but give them different effects. And get creative with the AoE to make the player consider positioning.