It can most likely be done with custom mip maps of the texture and swapping meshes but… there are probably more low hanging fruit that can be optimized instead? 
Maybe an additional optimization step using custom mips could be to lower the framerate to save a little bit more memory, but that depends on if you can tell Unreal Engine to disregard MipLevels on texture load to skip mips above level X - not sure about that 
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