I've modified the playeraccess engine file to remove the hard coded developer access, and instead provide flag based access.

INSTALLATION
* Simply install this file over the distribution version.  You will need to ensure that you also replace it for future updates (after checking for any changes).

USAGE
* Set the cvar for which access flag gives dev access.  I recommend using one of the custom flags (so you can give devs access to war3admin menu without access to other admin commands) - default is 0 (off - no dev access granted)
- EG: war3_dev_access_flag "custom6"

* Give your devs access to that flag in your admin cfg.
- EG: (admins_simple.ini):
"STEAM_0:1:XXXXX"              "20:t"                     //Remy - The "t" here is the custom6 access flag which would mean dev.

I tried it in there, however it seems that initplayervariables is called before the admin flags have been fully processed, so it can't test for the flag...