I just installed a feature that depends on Sapphire 8.x.x.x on Eclipse Mars.
After adding the update site for 8.2 installation went smooth and the feature worked.
But in the error log I found the following error message:
org.osgi.framework.BundleException: Could not resolve module: org.eclipse.sapphire.modeling 
Unresolved requirement: Require-Capability: osgi.ee; filter:="(&(osgi.ee=JavaSE)(version=1.8))"
From my understanding the following happend:
The custom feature has the following in its feature.xml:
<import feature="org.eclipse.sapphire.osgi" version="8.0.0" match="compatible"/>
because of this entry the feature org.eclipse.sapphire.osgi_18.104.22.168506110935 was installed. This feature has the following entry in its feature.xml:
<import feature="org.eclipse.sapphire" version="8.2.0"/>
Because of this entry the feature org.eclipse.sapphire_22.214.171.124506110922 was installed. This version requires Java 8, hence the error message.
I think the correct entry in the feature.xml of org.eclipse.sapphire.osgi_8.2.0 should be:
<import feature="org.eclipse.sapphire" version="8.2.0" match="equivalent"/>
The value "equivalent" would also accept the version 8.2.1, 8.2.2 etc. The value "perfect" might be even better, as it only matches 8.2.0.
IMO the missing match attribute is wrong (as match="greaterOrEqual" would be).