I started a project like this in unity with newtonian physics in mind.
The biggest issue I faced was float imprecision (you can’t replicate a moving world around origin). There is also the issue of AI and physics. It will be harder to implement than you think, without understanding and implementing things like PID-controllers, etc.
Basically, it is a lot harder than it seems, but I would still recommend UE4 for the job, due to source access mainly. And if you will keep this as a smaller scale thing server side, UE4 already have a very robust server built in.