I really want to have them sign a contract that I can drop in the scope, schedule and proposed fees to provide some protection for me.

You will not have the rate long enough for it to interfere with your current and proposed profits.This is where having a good team comes into play for example having a seasoned realtor who knows the market on the purchase/ARV side.

If the proposed loan is too risky because (1) chance of default is too high and or (2) cost of foreclosing too high or time it takes too long and we would otherwise decline the loan, we might offer to purchase the subject property for a price equal to the loan amount.  

And you're proposing to pay the investor a "return" of 6.30%, how did you come up with that number?

They still all use standard HUD forms though l imagine.I'm curious is it federal,state or county legislation that creates changes between HAs?

Of course your participation in those tulip bulb type speculative frenzies isn’t guaranteed since the asset/product you are proposing DOES have real value.  

CA, in total continues to lose 100k's of population and continues to add onerous legislation, including the state rent cap they passed a few years ago (doesn't apply to sfr's though).I am not sure why anyone would want to jump in the deep shark infested waters right before feeding time, unless you have a clear proven strategy, or a very long time horizon.

Short-term rentals are becoming oversaturated in certain markets plus anti-STR legislation is resulting in some of those properties also converting to long-term rentals.You already have the operations experience by self-managing.

What you propose is certainly less risk than what I had envisioned. 

They can inform you of the process and the chances of your proposed use getting approved by P&Z and/or City Council.