Fire Emblem Heroes’s actual maps are already this unless they’re disqualified by all the RNG still being there, just punted into character recruitment
My feelings on this are informed by the fact that, at least until relatively recently, I doubt Fire Emblem was ever really intended to be a super number-crunchy, min-maxy, mathematically-consistent puzzle/strategy hybrid-type game, and, speaking only for myself, I don’t really want it to be, either.
The random elements are there to make each playthrough unique and to prevent (or at least greatly-mitigate) the potential for any given Fire Emblem title to become a solved game. Clutch hits, crits, dodges, and skill procs, by player and enemy units both, do create surges of excitement in the moment, but on a longer timeline, they also serve to keep maps from being entirely predictable, to make sure there’s always a chance for something unexpected to happen to which the player has to adapt on the fly.
Speaking less ludologically, it also helps to create interesting stories in each playthrough, which is also a reason permadeath was incorporated. Those clutch, unlikely moments in battles are also big moments in the “story” of your playthrough; the time when a character met a shocking end at the hands of an unassuming foe, managed to escape what looked to be certain death by the skin of their teeth, or made a big breakthrough in their training with a perfect level-up.
I don’t mean to insinuate that you’re not supposed to be engaging with the gameplay systems on a deeper level at all, because you clearly are, but I also don’t think Fire Emblem has ever really been balanced around the player taking the gameplay really, like, dread seriously, at least not until stuff like recent Lunatic modes and such.
I guess my big conclusion here isn’t that I think a minimal- or zero-RNG SRPG is bad or undesirable, but that I think it runs a bit counter to Fire Emblem’s identity and design goals as a series, at least by my assessment. I think the RNG is actually a pretty fun addition to Fire Emblem provided you don’t take it too seriously and are willing to take the good with the bad. That said, I also know that it isn’t going to be to everyone’s tastes, and that’s alright, too. Different strokes and all that.