It's a bit less than alleged difficulty if I'm not even struggling with it to begin with. I use the term alleged difficulty because in my opinion this job has no overt difficulty to speak of, but I would have liked to respect the opinions of people that do find it difficult. I don't have to struggle with something to dislike it. Separating combo buttons is not overly a "simplification" so much as an alternative. I would appreciate if you do not assume what I find difficult and not difficult: especially this already very easy job.
Do not tell me about target audiences. I am very familiar with the game catering to people that don't main the jobs they're reworking as somebody that dislikes the DRG and AST reworks. What I am asking for is simply an option. Where jobs like Monk, Dragoon, and Astrologian lost what made them special for a lot of people with no option to go back, I would simply like an option to find a really monotonous and functionally slow job more enjoyable to play.
You are overcomplicating this very simple "four combo system" severely. It is not even close to asking to change cast times on Black Mage, because that would fundamentally change how the job plays while all I'm asking for is a quality of life change even less significant than removing Huton from a job that functionally never had to press it. Monk has a flexible combo where your three-step combo can flexibly go between the routes and Viper can do the same thing. Dragoon can change different buttons depending on which combo route was built into and hypothetically Viper would be able to do the same thing. I wish I could make a gif to explain to you how simple this would hypothetically be, but all I ask is that you take a look at the jobs I know you already have levelled and see how easy it would be to translate what they have to this job.
In case you're still not getting it:
Monk can freely press any combination of opo-opo, raptor, and couerl combo buttons. You can hypothetically press Dragon kick into Twin Snakes into Demolish but you can also hypothetically press Dragon Kick into Rising Raptor into Demolish.
This is not unlike Viper where you can hypothetically press either stage 1 fang (Steel Fangs orDreadReaving Fangs) into either stage 2 sting (Swiftskin's Sting or Hunter's Sting) into either stage 3 positional (Hindsting/fang or Flanksbanesting/fang).
Dragoon's button conversion is conditional. If you build into itsDisembowelSpiral Blow combo then Fang & Claw will be converted into Drakesbane after Wheeling Thrust. If you build into itsVorpal ThrustLance Barrage Combo then Wheeling Thrust will be converted into Drakesbane after Fang & Claw.
Hypothetically, Viper's button conversion for stage 3 positionals could also be hypothetical. If this option were to be available, the third button would simply convert into a hind or flank depending on if the previous combo action were swiftskin's sting or hunter's sting.
You are massively overhyping what is a conceptually not very unique "four-button combo system". Viper at its core has two flexible routes not unlike monk. By your logic, Monk has a six-combo system by virtue of the fact it can flexibly go through these routes.