The answer I would prefer to give is that you should probably use a Suite/Advanced UI project for this. They are a more robust combination of what InstallShield has previously supported with prerequisites and chained packages that should allow you to more closely define what behavior you want to see. It leverages a more canonical form of package chaining that typically has fewer problems than the embedded chaining that is available to the Basic MSI project type.
However the transition to Suite/Advanced UI projects is not trivial and thus may not be reasonable late in a release cycle. Typically a dependency is a hard dependency so failures are not really optional. If you want to avoid the rollback, hard dependencies are better specified as prerequisites instead of chained packages. Soft dependencies are rarer; you may have some luck turning them into prerequisites as well.
