Now on completion, any cash contributed by the LLP or GP is rewarded firstly, say 8% IRR compounded if it can't be paid out from cash flow year 1.  

Start your own business and invest in Roth IRAs asap because compound interest is your friend.

Foundation issues, stone wall bowing outward.  

Pulling out the equity will not work on this property, it will only compound the problem.  

You can't eliminate the taxes, but you can delay them until retirement and earn compound interest on your tax money instead of letting the government earn on it.

That number will be compounded. 2.  

This situation is further compounded by the fact that there are a few properties which are similar to this scenario which I would also like to us him to fund. 

In addition to the 2.125% interest you will pay on the 401k, there are two "hidden" costs to this transaction: A) the opportunity cost of not having those funds within the 401k and compounding interest, and whatever your tax rate is.When you borrow from a 401k, there are no taxes or penalties assuming you pay off the loan properly.  

I think too often many of us want all the answers to our dreams packaged and presented to us with a nice little bow on it (not speaking to anyone on this post in particular).

If you're dealing with wacky compound loads, you need to be talking to an engineer... period.