NFD

Docker is an industry standard for deploying software on another platform. Docker supports CentOS7. Ubuntu-based NDN software can be packaged into a Docker container (that internally has a Ubuntu image), and run on CentOS7 host machine. NDN software running within Docker is as fast as running natively, and does not consume more memory or CPU.
Is there any reason your deployment cannot use Docker?

They would like to avoid extra maintainace overhead if possible.
Any reason not to support these platforms?

They would like to avoid extra maintainace overhead if possible.

What "extra maintenance overhead" are you talking about? It's industry standard to use Docker. There's nothing more to maintain. Developer provides Docker image. Operations team pulls the Docker image, and don't need to change anything. Moreover, operations team doesn't even need to understand how to setup NFD, because it's packaged in the Docker image.

Any reason not to support these platforms?

As you said, Boost is too old.