[KadabraZz]

Hello, you can change the skybox using the stripper

modify:
{
	match:
	{
	"classname" "worldspawn"
	}
	replace:
	{
	"skyname" "urbannightburning_hdr"
	}
}

I believe that there is no time to replicate a cvar for a client, I think that at any time it can be done.

#include <sourcemod>

#pragma semicolon 1
#pragma newdecls required

Handle hTest = INVALID_HANDLE;

public void OnPluginStart()
{
    hTest = CreateConVar("your_cvar", "1", "Hacked by plugin", FCVAR_CHEAT | FCVAR_REPLICATED);
    RegConsoleCmd ("sm_test", Command_Test);
}

public Action Command_Test(int client, int args)
{
    SendConVarValue(client, FindConVar("your_cvar"), "1");
    return Plugin_Handled;
}

This code is not mine but it works, remembering that you cannot replicate all cvars, there are some specific ones. Commands too, like r_screenoverlay