Alright, I have already surpassed all paths (even the impossible) with some or no remedy. While the boss battles is somewhat lower in health, their triggers is to be kept in mind. That department will be tied to my entire intuition, as I can beat the raid battle extreme mode by myself. The nightmare mode, while like extreme mode, I happened to witness a preview of the Spike Shot special attack. A whopping 2k per hit. I would estimate 4k in total, not to mention that the mafioso must be tolerated to live during the battle. Hopefully, there is a remedy to withstand that constant threat as there is 100% chance risk of exposure.
Getting back on-topic, in the Impossible path, each monster that you voluntarily battle is in level 50. Topping that, the health (rating) value can help to end and fail your expedition, thwarting your attempt to acquire your eel loot. However, should you win a voluntary battle, you have a chance to gain some eels along the way. I recall about 2 or 3, but every amount helps in buying inventory from the eel trade shop. The health value, as I mentioned before, can cost your turn points to disappear by a 20! Or so at least from a player (that being me) who started out a while ago (and might not have the right characters [or investment condition] to quickly dispatch the monsters). I know, for a fact, that enmity-based skills/attacks, will not work too well due to health percentage requirement and output not fast enough for turn point cost efficiency.
Now you know of the issue, the question is how to exploit these opportunities with enough turn points intact to finish the expedition? We have to keep the turn points in mind as if it's the timer in the Super Mario Bros console game. Because most of us players who prefer the higher rewards, I will focus of the impossible path. For each action taken, will cost turn points. Since the boss battles are the most expensive, the assumed turn points expense means that you must finish the expedition with less than 100 turn points. Each costing OVER 20 for the barely managing. You'll know if you barely manage after you beat raid battle extreme mode (or even higher!) without request for backup. Not a free ride of an expedition, now is it? In addition, there's the eel schools stage, where each fishing period costs 5 turn points. On the positive side, this is your chance to reap your rewards for additional eels so make your coordination and dexterity count! A few fishing spots might cost you 10 to 15 turn points. That's 70 to 85 turn points left. There's another stage called naval mines. This stage costs the least turn points, but comes with the risk of ambush, resulting in a mandatory battle. For me, each ambush is about 20 turn points. I myself am left with 50 to 70 turn points given the current situation.
I can probably safely squeeze in just one voluntary battle without getting booted. The thing is that some monsters don't provide the eel loot, such as a chance with the crabs. Their health is the lowest despite their numbers. I recall that a certain penguin gives 2 ells. Maybe I will go with one monster encounters next time as it would be easier anyways. If I should iterate the point, I'm trying to earn MORE eels from voluntary battles in the impossible path under the constraint of the turn point limit. Any ideas? Even if your solutions or findings won't match my given equipment/preparation/findings, I would like to know how others deal with these opportunities. Your input may help determine the worth of voluntary battles.