I had the same concern some months ago and if (if) i remember well, it was not possible, due (?) to the way params are merged thru the arbo.
[EDIT] This is what i talk about : "params" from config.toml in component seems not being merged
My only solution was to have my own namespace, and a README if people wants to override it.
You can have a look at https://github.com/divinerites/plausible-hugo and see how this works for me.
You can even have a partial for checking if all is correct (see plausible_check.html)
But when you add some [params.yournamespace.xxx], those [params.yournamespace] and al. in your theme are no more available. So you have to give them again (the default option is really helpfull tho in this case)