Roughly in order of importance:

1.) Move off Vagrant and use VirtualBox directly
2.) Multi-project (multiple WordPress installs, single site or multi-site),
3.) Installer for macOS and Windows
4.) Move from 'services' to 'stack'
5.) Full CLI (update to box command line tool, ideally GoLang-based)
6.) Include all potential installables - reads an installable.json enables for project
7.) Orchestrator ("Orca" - ideally GoLang-based),
8.) Implement REST API to configure container ("Barnacle": Configures PHP extensions for processvm, databases for dbserver, websites for webserver, etc.)
9.) Box API (ideally GoLang-based),
10.) Incorporate SyslogNG
11.) Incorporate DNS/Squid proxy, etc(?)