If there's already an instance open of an application it would be preferable to have that application receive focus instead of launching a new instance. That way Jarvis could be used to quickly to switch between applications in addition to launching them.

A key combination could force a launch of a new instance. Shift+Enter would be in keeping with the Windows default of launching new instances when shift-clicking an application on the taskbar and when using Win+Shift+ to switch application on the taskbar.