Yes in general, with a big "BUT" coming...Is this sort of thing something you would be interested in? If so, what would you like to see in it?
I'm actually okay with this; even if some stuff is reprinted, having everything in one place is, as you say, convenient.
- The fighter class reprinted for convenience
Not interested. I'm actually not a big fan of subclasses. Rather than "customization" my feel has been they make your character cookie-cutter... your subclass character is exactly the same as every other subclass character. And you probably have abilities in your "ability set" that you don't even want.
- 50 (?ish, maybe not that many) new fighter subclasses
As long as they are mechanically unique, this interests me.
- New equipment, weapons, armor
Tell you what, give me 50-ish new Feats - something EVERY subclass can use - instead of 50 new subclasses, and I'll be happy. A Feat is potentially applicable to EVERY subclass. This is the opposite of subclasses - universal instead of super-niche.
- 20+ new feats
Depends on what these rules are. For example, I'd love to see more advanced combat maneuvers, perhaps tied to weapon classes like axes, spears, etc.
- Optional new rules
Having 40+ years of experience, I don't know that I'll see a lot new here, but I'm not actively against it. There are far more players newer to the hobby for which this will be new ground and I want to see new players get excited, too.
- Role playing advice, seeds, hooks, etc. to make your fighter your own.
We have different plans for A5E, starting with Secrets of the Tome this year.I'd rather it was for A5E,

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.