EzekielRaiden
Follower of the Way
My perspective is, people didn't like splitting up races and classes into multiple books. That's a thing 4e did, giving "the whole game" in one sense (1-30) but "only 1/3 of the game" in another (about 1/3 of total classes, 8/25.) This was widely criticized by a number of critics; I don't know if that means it could've gone over well if the presentation were better. But I'm inclined to think the answer is "no".WotC says 10% declining to 1%.
I may not cut the game to level 10 but woukd consider it at least.
As I said in OP not sure if 5th level spells are peak power or you would get level 9 spells at 9.
My homebrew goes to 5. I'll extend it if required but it's just more work.
So perhaps the reverse path would work better. Promise folks that more levels are in the pipeline, but that the focus of design is on the levels everyone plays. Then it's "1/3 of the game" in one sense (levels 1-10), but "the whole game" in another (all "expected" base classes and a few extras for spice.) That might make people feel like they can be certain they'll get something like what they want, and thus as long as they like what they're seeing at level 10, maybe they'll like the future content for 11-20 too.