Indeed, snap confinement can be tricky to get right, in particular with applications like yours which look to require a lot of ambient authority in the system (ie the ability to browse all files on the system).
Can you please let me know whether you snap would also require the ability to modify arbitrary files too? In that case probably the only solution would be classic confinement. In that case you may wish to consult Process for reviewing classic confinement snaps to understand the kind of information which is required for snap reviewers to determine whether this is valid to grant for your snap.