Now to get that supported several additions steps should be done:

To activate dropins reconciling you need to do the following:

• open
  studio/configuration/org.eclipse.equinox.simpleconfigurator/bundles.info
• find the line
  org.eclipse.equinox.p2.reconciler.dropins,1.1.0.v20100525,plugins/org.eclipse.equinox.p2.reconciler.dropins_1.1.0.v20100525.jar,4,false

and change it to
org.eclipse.equinox.p2.reconciler.dropins,1.1.0.v20100525,plugins/org.eclipse.equinox.p2.reconciler.dropins_1.1.0.v20100525.jar,4,true

• create the studio/dropins directory and add plugins as is usual
• start JBDS with the -clean option at least once

To eliminate this steps plugin org.eclipse.equinox.p2.reconciler.dropins should be marked as auto started in jbds-all.product definition which is used to build JBDS product