You are talking about the source level only, correct? The binaries would still be running on a 1.7 system?
The reason why I'm asking is because I believe that Virgo as a server-side technology runs most of the time on "conservative" systems, i.e. systems that are not necessarily running the latest release from every software or OS. With such use-cases in mind it is sometimes better to stick to an older version, but that really depends on the consumers.
And even with a 1.7 compatible bytecode there are sometimes cases when it doesn't run with older class libraries. In RAP we are using the (maven) animal-sniffer plugin to ensure a certain Java class library level. Does something like that exist in the Gradle world?
Just some random thoughts...