[1.12.2] Changing the textures of a block at runtime

I'm trying to create a kind of pipe for my mod in forge 1.12.2, simply put, it should visually connect to other pipes (e.g. if there is another pipe above it, it should visually connect to it)

I've got it set up so that the nbt data of the block is set to the sides it should connect to, an example of this being

connected_down=false,connected_east=true,connected_north=false,connected_south=false,connected_up=true,connected_west=false

I'm aware I can change the model based on nbt data through the 'variants' of a json file, however, according to my calculations this would take 64-ish different models for each combination of the nbt states.

A simpler way would be to have a model divided into segments (center part, part that connects above, etc...), and toggle them on and off by assigning either the main texture or a secondary, transparent texture, based on the nbt data. For example, something like this would connect to the north but not the south (removed other directions for simplicity)

"textures": {
   "central": "gm:blocks/main",
   "northconnect": "gm:blocks/main",
   "southconnect": "gm:blocks/transparent"
},

Is there any way to achieve this?