About to head to Eryth Sea.
Question about Riki:
Is it just me, or was Dunga trying to send someone who's pretty clearly a high-functioning autist on a suicide mission just so he didn't have to deal with him anymore?
That's kind of messed up, yo :(
Especially since it's implied that he does that every year.
Aside from the fact that Riki isn't autistic at all, I'd say that the situation is less about wanting to off him and more about trying to get him out the door so that he can start earning his (and his massive family's) keep. Riki is basically the Nopon equivalent of a middle aged worker who somehow wound up with Hero as a day job
I really need to stop going for the Battle Masteries in Super Robot Taisen: Original Generation. They make the game way too hard. Especially when it sets the game to hard mode. I'm on Mission 18 and I could not figure out how to sink the Kurogane in less than 7 turns. Maybe I should upgrade my pilots...I don't think I've done that even once yet...
It's a little late to say this but if you're having trouble you might want to invest in fully upgrading an M95 Machine Gun or two. After that I'd suggest focusing on building up finishers and attacks used frequently as well as the usual suit upgrades (although I'd hold off on getting too wild with them early on due to eventual mid-season upgrades).
If you're looking for pilot upgrades, I'd highly recommend giving Irm/Katrina (depending on which route you took) the Attacker skill ASAP along with Ryusei/Kyosuke and Rai/Excellen (if you're at chapter 18 you probably can't afford more than that). It's debatable to say whether investing PP into Infight/Gunfight over stats is the more preferable option, as stats yield higher damage boosts for less but Infight/Gunfight provides an extra space of move/an extra square of weapon range at levels 4 and 7 respectfully (I'd say, bother only if they don't already have the skill and only up to level 4/7). All support pilots (i.e. Garnet/Russel, the battleship pilots, Aya/Radha, etc) should aim for SP Regen, Concentrate, and/or SP Up.
It's kinda hard to really recommend what to do beyond that since I don't even recall which route you're on nor the pilots at your disposal. Generally speaking though, your best option is to go all out with Accel, avoid using as much SP as possible early on in the stage, make sure to ice as many grunts as possible by the end of turn four to build as much Will as possible, then send everybody to dogpile the boss.