You keep pushing away namespaces but (as I'm sure you know) you can make a thread join a namespace. I do this with network, mount and user namespaces, to get some separation and be able to put strict firewall, mount rules in place.

Since you can put uid and gid in firewall rules it makes for interesting belts and suspenders component separation.

Combined with ZeroMQ, and SPARK and lots of generated code for the inter-thread comm and you can build modular designs.

Just don't look at you ip link / ifconfig :-)