I think I would reinforce the foundation with steel rebar for additional durability, it actually adds a lot to the breaking strength of the structure. Container homes are pretty strong and safe, also eco-friendly, so reducing the cost and increasing the speed of the construction by using steel coupling is the best piece of advice I can give here, there is one company I can certainly recommend for this:
http://www.hardman-de.com/contact.html Overall, it's a fast approach to building, also reliable.