I would not like to see mandatory anything, however I would like to draw attention to this MAIB (marine accident investigation branch) report. The small sailing yacht Ouzo was sunk by a large ferry. The likelyhood is one of the crew survived over 12 hours in the channel before succumbing to the elements. They did not have an ELT, raft or a yachting equivalent of a flight plan.
The principles apply equally to recreational aircraft.
Everybody has choices to make and as an aircraft commander you make choices for your passengers as well because they dont have the skills and training to make those decisions for themselves.
Plenty of crashes are survivable and when your on a hillside with multiple injuries its a bit late to wish you had told someone when and where you were flying, infact you might regret it for the rest of your life.