Hi Michal and Marc!
I suggest to merge it with cookies, add a config variable to enable it but disable it by default, adding appropriate warning about the security implications.
I agree with Marc - when first trying the new method out, I was quite confused on how to use it, so maybe less-experienced users will get a headache from it. Maintainability with this auth-mode should be easier as well, I don't see any real drawbacks when merging it with cookies with an ability to turn it off.
Regards, Garvin.