Good license(s) for specifications?

Suppose I am writing a specification, let’s say a file format that I came up with. I’d like others to liberally make use of the spec, so they can create interoperable software. The license should not impose any restrictions on implementations (they can be proprietary if so desired), and also allow liberal re-use of the specification itself (for example for internal documentation, but even commercial use for all I care).

Given the above, CC0 or such come to mind. The only thing that I wouldn’t mind keeping control over, though: if someone makes a derivative, slightly incompatible change to the specification, they should be required to change the name, to avoid confusion.

Is that a reasonable concern? How could I address this in the license? Or is this actually entering trademark territory?

I think that this is probably in the realm of trademarks rather than copyright (trademarks govern the use of names and branding, copyright covers works).

I think for specs this is probably a reasonable thing to do without any particular worries about infringing on the free software spirit, but note that if you use trademarks to enforce this kind of thing on software distribution you’ll be in violation of the Debian Free Software Guidelines (which is a separate thing from free software but matters for practical purposes as far as Linux distros think about what software to include).