My mod Dark Utilities has several blocks which can be camouflaged to look like other blocks. To help maintain the illusion while Waila is installed, I override the getWailaStack method to return the held camouflage block. When Waila Harvestability is installed, this will cause the mod to throw an exception which is caught by Waila. The following is the exception that is caught.
[19:57:59] [Client thread/WARN] [Waila]: net.minecraft.block.state.BlockState$StateImplementation.getValue:137
[19:57:59] [Client thread/WARN] [Waila]: net.minecraft.block.BlockStone.getMetaFromState:89
[19:57:59] [Client thread/WARN] [Waila]: net.minecraft.block.Block.getHarvestTool:2300
[19:57:59] [Client thread/WARN] [Waila]: net.minecraftforge.common.ForgeHooks.canHarvestBlock:136
[19:57:59] [Client thread/WARN] [Waila]: squeek.wailaharvestability.WailaHandler.getHarvestability:123
[19:57:59] [Client thread/WARN] [Waila]: Catched unhandled exception : [class squeek.wailaharvestability.WailaHandler] java.lang.IllegalArgumentException: Cannot get property PropertyEnum{name=variant, clazz=class net.minecraft.block.BlockStone$EnumType, values=[stone, granite, smooth_granite, diorite, smooth_diorite, andesite, smooth_andesite]} as it does not exist in ExtendedBlockState{block=darkutils:sneaky_ghost, properties=[]}