I understand you now. I suppose the argument is you're building a house without a door. While you may believe you have everything you will ever need in that ho

I understand you now. I suppose the argument is you're building a house without a door. While you may believe you have everything you will ever need in that house, there's a likelyhood you will eventually need to leave (or something needs to arrive). Now you're stuck. Of course, it's not all or nothihng when it comes to IP space. If you were going to use 11.x for an air gapped secure enclave, I would have a very difficult time presenting a scenario where that may bite you later. However, I'd vote to use CGNAT reserved space before any 'unused' public IP space.