I agree, this is a big one. It has been mentioned in other places as well:
I have a similar situation as others in this topic. The studio can load plugins just fine upon opening, as long as an appropriate proxy is configured. But then you cannot execute against any offline applications due to the proxy 
Is it true that the studio has to reload plugins every time it executes? In other tools, like JMeter, the standard procedure for me was to either:
1.) Configure a proxy to access a plugin store, download my plugins, then remove the proxy config.
2.) Manually download/install the plugin
In either case, the studio MUST be able to use local copies of the plugins, instead of accessing the plugin store every time it’s opened.
In the meantime, I will have to use a 5.0.0 version of the studio where basic reporting was built-in This was actually one of the reasons I held off on updating my studio in the first place…