That sounds like one-way sync which I really hope is coming with 2.0.
I like to have a full offline backup of my Google Drive (incl. Google Docs converted to MS Office) in one of my VMs which doesn’t sync back any changes. That way even if something goes wrong (e.g., ransomware encrypting backup files, Insync bug messing up files or creating duplicates) the files on Google Drive are safe.
The difference to OP’s request is probably that with one-way sync, locally deleted folders should be restored immediately with the online version.