What's left to do

Technical

use bundle package instead of bundle install --deployment see the Documentation on gembundler.com
respect offline mode
check binding to lifecycle (generate-resources): which configuration is really needed in teh simplest case?
consider using namespaces (maybe we shoud call them "gemsets" bc they roughly do what rvm's gemsets do)
handle bundler groups in some reasonable way
make running ruby-based tests with declared gems using mvn test