Well, I'm still at area 1 - just beat area1-5 boss (if you can call it), but still haven progressed much into battles. Actually I've been replaying Area 1-3 repeatedly, to get some good 20k Meta Chips per battle, at almost 40+ consecutive battles.
So far, I've progressed the game story wise till as much as I can. Most characters at 70+ percent complete, besides Gouto and some other characters - as it's required to finish 2-5 or 2-10. I unlocked all the available Mystery Point that's available to me, with a couple dozen MPs laying around lol. Most of my characters in battles are over level 20, so I think I'm good to proceed... as I've upgraded ton of them. Looks like I can also upgrade the Sentinel itself later on, but right now it's still locked.
Reason I've been replaying the 1-3 is to make myself more comfortable in terms of strategic deployment of my units - but it seems like some scenarios it's limited for just a few sentinels to go out (like 1-5 boss battle) to get that bonus - and what they can do. Small swarm of workers is best delt with someone like Yuki, with armor upgrade and multi lock missiles - although it's pretty apparent that how underpowered (besides leg spikes) Gen 4s are against the big foes. Also trying to make better use of the long-range Gen 3s - but just like anything in life... I love using Usami and Miura's nuke attacks! (both maxed out) - it really clears out ton of stuff, although it takes a lot of EP, and sometimes perhaps due to fatigue, Usami and Miura doesn't even start with enough EP to fire that big ones... but it does wonder saving the city. Thanks to them, 1-3 scenario, I cleared initially around 9-10% city destruction - but now I can get them done as low as 3% lol...
Some of the attacks, like Megumi's Orbital thingie - I am not so sure what it does or how powerful they are. Trying to learn what each attacks do and some are quite interesting. Miniami's anti-air bombardment is quite powerful, but has pretty limited range. But once they connect, it somehow extends the range... but I really have to anticipate how enemies move, and that kind of anticipation isn't something that you can do in first try but knowing exactly where and what types of enemies would appear. I'm trying to save up some Meta chips for other ones like Missile Rain and all - wonder how good those are. Gravity missiles as well. So yeah - right now Minami, Megumi and Shinomura's sentinels are more difficult (?) or unique to use as some of them don't have that killer moves like others... but since there are plenty of heavy hitters - not much issues have arised yet.
But maybe because I am so OP'ed, battle is pretty easy to get S rank, and I'm a coward to up the difficult at the moment. LOL. (They all seem to have some terrible things going on in their lives, so I feel horribly bad upping the difficulty level on them as well)
Not sure what other stages would offer better farming of MPs - I think I will start progress till at least 2-5, so that I can get some more of stories out of remaining characters.
... I think it will take me like 100 hours to finish the game. lol...