How can I change permissions from www-data to other groups on VDS?

Question

Apache HTTP Server

There is a VDS on Ubuntu 14.04
Apache2 runs under the www-data group. More than 10 developers can work on VDS. Accordingly, a question arose.
It is required for each site to assign its own group of type sitename1, sitename2 and add ssh users to it.
The problem is that the same CMS (Bitrix, Wordpress) when changing the group to the project folder and files, respectively, stops saving changes from the admin panel.

Answer 1

put some module like apache-itk so that each site can work from its own user

Answer 2

Each apache2 virtual host needs a separate group.
Look here sys.dmitrow.com/node/87

Answer 3

Add everyone you need to the www-data group, don't bother the bikes.