Well Unreal 4 has changed a lot of the “rules” so to speak by not hard coding limitations which usually resulted in the development of lower fidelity assets that even if one wanted to go hi res so to speak due to the demands of the game engine. The result as to this form of making assets to fit into the 3d space is what would be called a “fit to finish” asset the left little or no room for what I would call “Next Gen” development of a working asset if one did want to scale up their project due to the fact that you can not make not enough do more yet on the other hand Unreal 4 needs a rethink as to the process of asset development that is not typical of most if not all “game” engines
UE4 being whats called a closed edit environment then it should be the job of the environment to add features in app that will allow the art to scale as to the needed output by replacing the process usually done as a “fit to finish” process.
For example.
One can add Tessellation if there is need for more detail for things like displacement maps.
In 4.14 Auto LOD for static mesh was added so it can be assumed such a feature for skeletal mesh is in the future.
4K images should be used and materials constructed that outputs to the desired resolution with out texture resizing.
Overall though the fact the UE4 can parse the art means that decisions can be made with asset in hand and evaluated based on fact and not an assumption that building optimization into the creative process is still a requirement.
There is nothing NextGen about butchering the art based on ten year old ideology and I tell my guys make it the best you can do and once in game lets talk about it then. 