I don't really understand this point, even without an LP in place at all there'd still be the feeless books

AMM tech is provably superior to orderbooks in a lot of ways.
Without the LP the price of Zing can crash to near zero very quickly.
This creates a chain-reaction death-spiral where yield goes down on delegations so delegations need to be pulled as the price collapses.
AMM has exponentially more liquidity than an order book especially for a startup.
Not having the AMM locks everyone in and doesn't allow people to move in and out of the market at will.
This wouldn't be a problem if everyone was disciplined and willing to wait... but 99% of people want what they want and they want it now... while only the remaining 1% are the real liquidity providers. The AMM incentives create exponentially more liquidity providers than a typical orderbook.

I think staking rewards serve their purpose to reward those who delegated/supported us early

It looks like a reward on paper but it's actually a punishment in several ways.

1. It forces the money to be locked up for little reason.
2. Zing inflation is so high that the "reward" is completely dwarfed by dilution.
3. It now takes 1 week for the market to be able to react to pumps in demand/price.
4. It feels more like virtue signaling than an actually useful mechanic.

In my opinion it would be much easier to use that inflation elsewhere to increase the token price more than the 15% yield that's being offered. An x2 in the token price is equivalent to +100% APR for that year.

The thing that I fail to understand why it doesn't get mentioned in these discussions is that LP'ers get liquid zing daily, isn't that also something the providers can instantly sell for a hive profit or to increase their position by selling half and outgrowing people staking/delegating in a major way?

This is never how it works out in practice. If Zing has success number will go up and everyone in the LP will lose Zing regardless of the APR... because they are the ones selling the Zing to the new buyers. If Zing doesn't have success the LPers are just as fucked as everyone else... so they're taking double the risk for half the reward, and the only thing that makes up for it is the yield on the LP.

My target for LP yield on a startup moonbag would be in the range of 50%-100% APR. Any higher than that and it's DEFI 2020 hyperinflation all over again. 30%-40% is pretty good for the more serious yield farmers... and the number can get as low as 20% when the game has actually been playable for a while and gets some more stability. That being said this number needs to be a free-market mechanic. The number goes up and down with the token price, and you often will get what you pay for. Currently 9M Zing in the LP today. Is that enough? It might be. Then again if someone buys 5M tokens there will be very little Zing left for sale.

Again just to reiterate I think everything looks pretty okay at the moment.
These are just the changes I would make if I was in charge.
Not that I want to be in charge that's a pain in the ass as you well know.