clarity of concept

You could do that as a convention in the client library (have a function that takes one name and derives the others from it). There isn't a need for a protocol change for it.

It isn't necessarily good practice for services to have one object with everything in one interface anyhow, though it's probably fine for a very simple service.

The object names are only namespaced because a single process may contain unrelated modules. For example all GTK apps could have objects available under /org/gtk.

If you know your process doesn't have multiple modules you could name an object /foo just as you can have a global variable in C called foo instead of my_namespace_foo. What is "OK" is a judgment developers have to make.

There are also cases where a strategy like naming each object with a GUID or something makes sense.