Message "Incompatible, requires to upgrade system" is misleading. Indeed, it can be understood as if the current version of the plugin is not compatible (instead of the target version of the plugin is not compatible).
This message should be made clearer:
"PluginName X.X is not compatible with SonarQube Y.Y.
You need to upgrade SonarQube before performing the plugin upgrade."
(if possible, "You need to upgrade to SonarQube Z.Z to perform the plugin upgrade.")
This message and the plugin download button should be displayed at the same place (add a new column before the date one).