That's a really good idea. The height is good also on bathroom vanities and many are sold without sink.
They usually have great drawer & door assemblies. While many will have particle board sides. That could be reenforced rather easily. Common lengths are 30-36". I saw one in Costco that was dark stained Cherry? with a light grey granite sink. It would be perfect for a 18x18 cube maybe even 24x24 cube. The nice thing out doesn't scream PetSmart Asile #5.