Designing a game system and curious about what there is appetite for among this crowd. Comments would be helpful. Thanks!
I think you should aim to be authentic. Explain clearly why you do what you do and only include what you actually have used and played. Keep it as terse as possible.
Your challenge is not the design of the system but explaining in a way that somebody else can learn it. In the first couple of draft of my Majestic Fantasy Rules, I read some section out loud as I was trying to teach it. And some of it made me wince and think "Well wording that way isn't going to work".
Even now with my published Basic Rules heavily edited, I found a handful of sections where I wasn't complete in my explanation, or omitted something* because it was so second nature to how I run my campaign.
*Like how I award XP.
As for how popular it will be, as long as you are authentic, friendly and diligent, you will get a get at least a small audience. Beyond that is so random that the best you can do is to have a plan if it happens but don't count on it.
But with the cost of today technology and the way we distribute things now, you don't need a particularly large audience to do a nice project or to get a reasonable return (in downloads or sales) for your time.