Now some of mine are more commentary on designers than publishers but its fair to put in.
One thing I would love a game that hired an artist to just commission tons of profile images of characters that fit their setting. Especially for very unique settings. Its a great resource to put a face to an important NPC.
More publishers should embrace their role in making Character Keepers in various formats including Google Sheets but also the most common VTTs. Relying on fans to do so much feels wrong IMO - at least they should reach out to a fan project and reimburse them to polish it up. But it sounds quite idealistic given margins they have.
Touchstone inspirations/Appendix N should be a norm. I love reading and watching all kinds of related media to help me understand what tone/vibe/genre I am supposed to convey as the GM.
I think there is a lot of room to make character sheets faster and better. I love the cards you get with Starforged and City of Mist.
Ditching Justified when you end up with endless hyphens.
Rag Right reads so much better even if you don't have
perfect columns but instead I have way better readability. In general, they should research or hire people to improve readability (like having 45-75 characters per line) and accessibly especially.
Play examples would be much easier to follow if Player name, Character name and Class name all used alliteration and those with the same starting letter were not included in examples with each other. EG Gary the Game Master and Fred plays Fiona the Fighter. And names don't have to be anglo - even better if the example was based on playtesting.
Standard terms where you can. Flavor is great but if I can't skim and understand the core mechanics, its not setting the mood except frustration. Experience, Player, Game Master, PC, Initiative, etc. And I know Game Master is change frequently - its a small pet peeve of mine. Changing the term and acting superior that "oh in my game, they aren't a master" is acting deliberately arrogant and just wrong on the role of the GM in most games.
A list of go-to escalations and obstacles when my improv-ing chops aren't ready.
Keep your lore separated and put in the back of the book except for a summary. That microfiction mixing in makes reference EVEN harder.
PDF should have books, character generation and play should have examples.
No art behind text - again readability.
Avoid unnecessary technical or obscure language where common terms can do better. Don't have to go full 5e but there is a balance to be tested by your playtesters just reading it.
I love The Between's steps in the First Session. So easy to digest and well organized. And I love
CATS (Concept, Aim, Tone, Subject Matter) - its basically how you sell the game and making sure expectations are well and set - one of the MOST important things to a successful TTRPG. Any tool to help with that really is key.