Stand Alone Unit Control Panel (UCP) Location

It depends upon what the operator is intended to do while operating the panel. What does the panel enable to operator to do?

If the operator is controlling the function and running of the machine, he should have control. If it is totally isolated with interlocks to disable the machine if someone opens a safety gate and pages can be made with bells and whistles to warn of start-up, then control room can operate. If control room does not have all these capabilities and cannot directly see the machine, then only the operator should have control. Although the control room can still have monitoring functions. It all depends on safety factors and who is responsible for the safe operation of the equipment.

You don't mention how large this machine is. Some of ours were almost a mile long but had huge amounts of safety devices to keep people away and safe. This was run by our control room with closed circuit viewing. To prevent inadvertent starting of the equipment, controls should be located at the equipment so the person responsible can oversee directly the operation. We also set our equipment up that is started by our control room to have absolutely no overrides to devices. Local control has ultimate authority.

"any standard define the characteristics of the unit control system used to control package?"

One standard that is missing from lots of questions such as this is common sense.