We have downloaded the Eclipse JEE distributions and JBossTools site archives (and a number of other plugins in standalone or site-form).
When the developer starts our eclipse launcher, it'll unpack the relevant eclipse and run the P2 installer to add the configured plugins.
In the case of JBoss Tools, we only install a subset of the features: org.jboss.ide.eclipse.as.feature, org.jboss.tools.cdi.feature, org.jboss.tools.jsf.feature, org.jboss.tools.ws.feature, org.hibernate.eclipse.feature