I work with some projects on container homes with a container manufacturing company in Vietnam and the price is around 10k-15k for finished one (include plumbing, electric, flooring etc.).

Hey I'm sure you've found someone, but If not I have reputable contractor in Oklahoma that has been in the business for 20+ years in roofing & construction.

They provide a nice centralized marketplace for syndications, which could otherwise be tougher to find.Now that I know this exists, and due to the fact I’m accredited (so I can invest in all kinds of fun stuff more directly than ownership of a public equity) I am wondering if there are other reputable platforms that facilitate direct investment in other alternative asset classes.

You’re right, and I have a good reputation around my area.

In addition to choosing one with experience with 203k loans I would vet lenders and look at their local reputation.

Is it a greedy seller who wants top dollar for a pile of poo, or someone who is actually going to work with the guys/gals who are going to execute the project and have their butts/reputations/credit scores on the line?  

Justin, You can rollover your 401k into self-directed IRA, but not into HSA, which is Health Savings Account and not a retirement plan.There are several reputable providers here on BiggerPockets who are active on the forum, just search the forum for related keywords and you will find out who they are.

We also have a decent manufacturing base (Nissan has a huge complex, Berretta just moved here, etc). 

We have found it is much easier to resell manufactured homes on lease options.

I specialize in manufactured housing and some communities have the same problem regarding entrances.