I'm puzzled, too.  

I wish I had figured out the OPM piece of the puzzle at that point in my life...

Plain and simple.Look at the realtor as a smaller piece of the puzzle than you expected. 

I am wondering if some could provide a simple explanation, or point in the right direction, to help me understand what types of Syndications or other forms of joint but passive ventures qualify as the 'reinvestment' part of the 1031 transition puzzle?

What pieces of the puzzle am I missing?

Yes, it's only one piece of the puzzle, but you should know what your cash is making.

However I am puzzled because I was under the impression that a person can 1031 one property into, at most, three new properties. 

There are methods to minimize or defer taxes on income but it is a puzzle with many pieces.  

But it is one piece of the puzzle that perhaps isn't being utilized properly.  

Anything missed will be Change order.Timing- weather, zoning, city, off sites, neighborsTeam Members:Good commercial agent who understand retail and land developmentGC with experience in retail developmentsArchitect - same as aboveMortgage Broker- who understand SBA and construction financingLeasing Agent to lease up balance of spaceEvery market is different and a big piece of the puzzle for your development would be zoning, access points, services (deep).On the scale of difficulty- what you're undertaking is about a 7-8 in difficult in commercial real estate.