The rear seats should recline in addition to folding down/forward. This is essential when driving duty is being shared, so those not driving can get some shut-eye. It is currently very uncomfortable to attempt sleep in the rear seats.
This is a feature of most family cruisers we have encountered, e.g. Lexus RX series, Honda C-RV, Honda Odyssey, various other minivans. It does not seem expensive to implement greater freedom of motion with selectable stops.
Notes from Moderator:
If the rear seats are folded down, you can have an extended area that is flat that goes into the trunk. A number of owners have slept in this area that is far more comfortable than any partial recliner if using a cushion.
Minvans and SUVs typically have room to offer partial rear seat reclining feature, while only a couple of large stretch sedans offer partial reclining (Lexus LS600 comes to mind).
Tesla stated it may make an executive rear seat package for the China market, although it is unknown if this has been abandoned and/or if it would offer reclining.