My friends and I have played through enough Minecraft worlds that the game has in many ways become too easy, and so we've considered playing in hardcore mode as a solution. But, playing in hardcore is too punishing for most casual playthroughs. This mod adds a block called the Buy Station, which allows you to revive players in spectator mode at the cost of levels. Each time a player is revived their revive cost increases, adding increasing danger with each death, so dying remains punishing and failure is possible, without having everyone's fun ruined by random misfortunes.
For an even softer experience, consider adding Hardcore Revival
