Here is our first attempt at codifying a guide for style, development, and testing of EVM-smart contracts at Coinbase. https://github.com/coinbase/solidity-style-guide

Our goal is to build the best Solidity organization in the world and documentation like this is an important start :)

meh how do you inevitably deal with external integrations that don't want to use a pinned solidity version

You could just make the solidity version in the contracts more flexible but opens you up to making silly compiler mistakes

If anything it would be better to autogen the interfaces from the contracts so they can be used externally

I think that's fine. 

I just dislike the all too common practice of writing them for every contract in your project and inheriting. I think you should he inheriting as few interfaces as possible.