Lights and shapes are the only means of communicating a vessel not under command, which it would not be if the single hander is not/cannot be on deck maintaining a watch.
What other options do you suggest?
In short in the eyes of the law you do not have a right to single-hand your boat.
You do have a responsibility however to maintain a watch.
If you can't maintain that watch and/or are not able or willing to assume the responsibility for any damage you cause due to an improper watch it is your responsibility to make other arrangements.
It would be great from our point of view if the law had special rules for single-handers. It however does not.
Abby from the above link was sailing, she was stand-on, and was run down by a power boat with two people in the watch station. She was still found partly at fault by a judge. She was not on watch. It is as simple as that.
Another thought for you. Let's say you have 4 people with you. You hit a storm it's bad, lasts for three days. One guy gets seasick can't stand watch. The other three are exhausted due to brutal shifts. Frankly none of you are in any condition to stand a watch.
It don't matter, the rules are clear you either stand watch or accept your share of the responsibility for anything bad that happens while you break them.
The kicker is that if something bad happens the chances are almost 100% that at least some of the blame will fall on you regardless of what the other guy did.
That is the most important lesson I learned from the Farwell book.
Don't hit anyone or let anyone hit you because in the eyes of the law it almost always takes both parties both being less than perfect to cause a collision.
As far as I could tell by reading that book is than in the eyes of the law there is no such thing as an accident only failure of seamanship for both parties. They see their job as just to pick a percentage for each party.