Conditions:
* No operational radar on the target
* No friendly ships within 20km with a functional radar
* No stations within 30km or the station's radar range (lower value used: same logic as with vanilla distress calls)
If this all checks out, the target's emergency protocols will commence: drone pad will be brought to a working state, and all available drones queued for repair will be equipped, increasing the ship's defence strength.
The crew will also get really mad at you, and wont forget easily - better succeed once started, as a failed attempt might leave you with a ship that will kill any of your assets on sight - and which might belong to an otherwise friendly faction.
Any further actions against it will result in reputation loss - the skunk can only jam the identification and comm signals while boarding is in progress and the radar of the target is defunct.
Selling hijacked ships to a shipyard friendly to the original owner will have some annoying consequences - the shipyard will turn on you for a while, and you will have to pay for the ship as well.
Ships can only be hijacked once.
Anyway, yarr.
Workshop
dropbox
Steps to hijack:
0. You can start boarding just to get the info if hijack could work. A hint will display in-range ship/station and radar count. Cancel the ops.
1. If found a clean target, destroy the radar on the ship. This will drop your rep a little, but this loss is inevitable (and intended).
2. Start boarding. A hint will be displayed, either saying hijack started, or if anything moved in range then you will be notified about that instead (in that case you can still cancel).
If hijack could start, from this point on right until the op is finished attacking the target or its XS/S/M escorts will not hurt your rep.
3. Get rid of the escorts if needed, board the ship.
4. Try to sell the ship to a shipyard that is friendly to the original owner if you dare

Save safe.
Boarding Options is compatible, thanks to camus/Clownmug's help.
Incompatibility:Mods that keep spamming hints will also hide Hijack's messages.
You should still be able to see if hijack started from the target changing to enemy from its normal faction.