Hey @Louis Deconinck, I can try to help you. Right now it acutally is possible to restrict access to some specific storages. So what you could do is to restrict access to the request queue (e.g. access it under your own token hardcoded in the actor). There is an issue with that. To see the run, you need to be able to access all 3 default storages, so you will have to create additional request queue if you would like to hide it (and keep the default empty, but shared with the user).
Other possibilities: keep your headers in runtime memory only and add them to the request in the preNavigationHook (similar to what @luigi.ruocco described above).
I hope it help you with your case, let me know if you need some more help.