Currently, all boot features specified are installed in a single go: all the bundles get installed, resolved and then afterwards get started. This works fine for most features, but there are a few scenarios where it would be nice to allow installing the boot features in a few independent batches.
One example is ServiceMix' use of OBR in the features. You can install OBR support through a feature, but it needs to be installed before resolving the other features to allow the Features' OBR Resolver support to kick in. We have now worked around this in ServiceMix by adding the OBR feature's bundle to the startup.properties file, but it would be nice to have a simpler solution.
Another example is a feature that include a war: url for adding web applications. That requires the war feature to be installed and started before attempting the installation of the web application feature.
We could e.g. allow adding parentheses to group parts of the boot features that need to be installed in a single batch. Something like (obr,war),activemq,cxf,camel,jbi could install the 'war' and 'obr' feature in a first batch and the do the rest as usual.