In fact, if you use objects and textures from the game client, the choice of engine does not change practically anything. For example, here is a video on UE 2 (special custom UE 2, but.. The engine almost from the 90s). There is no such big difference with what they are doing now in the UE4 (IMHO)
This is more of an art work than an advertising one. In L2 business, everything depends on a dry and understandable conversion, and my case.. This is when you make a location for several days, laying out pebbles, cones and driftwood on it, about which the guy will run in 6 seconds.. Here we need an esthete who will pay for art, not for timing -)
xDD