I've already had two 'got away' on Priest of Yx'lokwa, after getting one of the four fish to mooch, to get one of the three fish to mooch for the priest... and it's a small but frequently repeated rare window, so I'll only have to wait an hour before being able to try again, which I have that luxury, now being a full time work from home person, my lil lala just sits and fishes on my laptop while I work, only needing me to reach over and hit a button when I hear the 'plink!' sound of a fish on the line, many other players don't have the time available to hit 12+ hours of fishing windows and some of the windows are still quite egregious (Duskfish is now 21 days away)
Surface slap does not work on mooched fish, and if the Big Fish you're looking for is from a mooch, it gets a bit rough on GP to utilize it, and if the big fish is on a mooch chain, it's only slightly helpful. If it persisted, some fish chains would get easier, but still not be a cakewalk, like the Great Serpent. Instead of 1/4 x 1/3, it becomes 1/3 x 1/2 by slapping away a Yellow Pipira or Robber Crab to get to the Priest eliminating them from both the initial cast and the mooch catch.
Some pools would get somewhat trivialized (look at Loch Seld in particular), but I'm talking about changing things from previous expansions and ARR.. this is all older content after all and I think it should get easier over time, because while realistic elements are nice and all, this is still a video game, and the purpose of a game is to have fun. Failing something just because of a random, uninfluenceable die roll, just isn't fun for me. I land a rare slippery fish (like Charibenet, which I landed two days ago) and it's not 'Yeah! I overcame a challenge! Woo hoo!' it's 'Whew, finally, I got it, now I thankfully never have to do that again.'
The La Noscean fish wasn't Faerie Queen, because I was working on it with Fish Eyes and I think there was no weather requirement, I was working on it for quite a while, an hour or two straight, maybe more.