After reading about modes of operation for block ciphers, I've found that basically all discussions about ECB end with: "never use ECB". For example this security stachexchange answer. However my understanding is that ECB is only insecure if you may send the same block twice. So, is ECB safe to use if I can guarantee that I never send the same block twice?
For example, suppose I have a home automation system where I have a number of commands that can fit in less than 8 bytes. I then append a unique 8 byte message ID to this data to form a 16 byte block. I then encrypt this block using AES128. Thus I would never send the same message twice as I never expect to give more than 2^64 commands. Also, say I use a counter as the message ID, then I would also prevent replay attacks.