The iPhone 6s Plus inherits a 7 out of 10 on the Repairability scale:

The display assembly continues to be the first component out, simplifying screen repairs.

The battery is straightforward to access. Removing it requires a proprietary Pentalobe screwdriver and knowledge of the adhesive removal technique, but is not difficult.

The Touch ID cable is still tucked out of the way, but is paired to the logic board, complicating repairs.

The iPhone 6s Plus still uses proprietary Pentalobe screws on the exterior, requiring a specialty screwdriver to remove.