I've got a number of plugins that have worked cross all the prior versions, from 2.0.0.2 onward.

I copy their folders to  server/conf/ccm/
and then add their provisioning profile

make sure the server will load them on restart and restart server..

but on 6.0.1 I am getting an unexpected error and not sure what the issue is..

2015-12-30 07:46:30,594 [       Launch callback handler] ERROR eam.repository.provision.internal.ProvisionService  - CRJAZ0285I Failed to connect to "file:ccm/sdsites/sd-advisor".
java.io.FileNotFoundException: M:\RTC60~1.1GM\server\conf\ccm\sdsites\sd-advisor\site.xml (The system cannot find the path specified)

if I cut/paste the file string into notepad++ I can open the site.xml just fine
M:\RTC60~1.1GM\server\conf\ccm\sdsites\sd-advisor\site.xml
this is windows, the server was started from command shell with server.startup.bat

M:\RTC60~1.1GM\server\conf\ccm\sdsites>attrib sd-advisor\*.*
A            M:\RTC60~1.1GM\server\conf\ccm\sdsites\sd-advisor\.project
A            M:\RTC60~1.1GM\server\conf\ccm\sdsites\sd-advisor\artifacts.jar
A            M:\RTC60~1.1GM\server\conf\ccm\sdsites\sd-advisor\content.jar
A            M:\RTC60~1.1GM\server\conf\ccm\sdsites\sd-advisor\site.xml

I don't see any windows permissions problems.