Right now, we only have production and local. A sandbox site (pulling code from a sandbox branch instead of master) would provide a nice middle ground for review and tweaking with stakeholders before pushing to prod.
Need to create another OAuth context in Civi
Need a db to add the new user preference tables
Guessing we want to be able to manage this by pulling arbitrary git commits, not the usual deploy process.
If we still can't run gulp on the sandbox machine, we'll want an additional option to run out of /src (like -d does) but still require OAuth.