Problem solved!
Found MinecraftByExample by TheGreyGhost, went to this class and found a comment at line 38 which said:
// NB If your block has multiple variants and you want vanilla to load a model for each variant, you don't need a
// custom state mapper.
// You can see examples of vanilla custom state mappers in BlockModelShapes.registerAllBlocks()
Checked out the BlockModelShapes file at net/minecraft/client/renderer and found all the vanilla custom statemappers.
Used this code to register my own custom statemappers:
public static void createStatemappers() {
ModelLoader.setCustomStateMapper(hemp_tripwire, (new StateMap.Builder().ignore(BlockHempTripWire.DISARMED, BlockHempTripWire.POWERED)).build());
ModelLoader.setCustomStateMapper(hemp_crop, (new StateMap.Builder().ignore(BlockHemp.AGE)).build());
}
Called everything through serverproxy.
Thanks for the help, sorry it took me a while to get a result! Really appreciate the code samples you submitted!