What flag is of your future vessels? What classification will you want?
Normally, your vessel will need to fullfil IMO requirements which are applied to container vessels with unrestricted operation.
You also need to meet requirements from the state whose flag is on your vessels.
You also need to consult with your classification society who classes your future vessels.
As usually, you will need something like main engine and other auxiliary in engine room and deck machinery.
If you need a handler to handle containers, you will need one or more container handler equipped on board the vessels.
You will need to equip a system called automatic anti-heeling system which is to, as its name says, keep your vessel in balance status automatically.
If you want your crew to be happy with cargo handling jobs, you may also need valves remote control systems and tank level gauging system.
If you would carry reefer container, you would need to equip container power socket system and might need a reefer container tracking/managing system to power your vessels.
Conclusion:
You may need to show your practical requirements then someone can tell you exactly what you need for your good vessels
P/S: Have you selected a shipyard to build your good vessel? If you haven't, should I seek an oppotunity to build your vessels? PM me if you are interested!