There is not much keeping you from making a amazingly detailed game,
providing the GPU can handle that*
with the exception of LibLoad/libFree bugs,
There are some tricks we can’t use, like instancing and static draw call batching,
other then that, the artists limits are blenders limits,
and publishing options.
About workflow - I have a addon in mind, but need help on the BPY side.
(choose actor type, choose actor armature, set animations names for actor type)
press p - > you actor is moving and playing animations
this will be less flexible then a rig designed by the developer, but not all developers are looking for something