Only thing Ive found inside the engine is split mesh, but that kinda splits it into thousands of pieces… and in a very weird way, even if I want to merge some back the dissections are not in the wanted position
Do you have access to the original model? If so, since you are wanting something very specific, it may be better to split the model in three in a model editor (blender, maya, etc) and bring them back into the engine to make a modular mesh. That will give you the most finite control.
Otherwise, check out this thread post that may have the answer you need: