Hello and welcome to the forum.
If your soldier dies, you can always recruit a new one... just in case you thought there are only the 8 starting soldiers.
Anyway, the mods usually just add new stuff to the game (weapons, craft, enemies, factions, missions, terrains, etc.) or try to make the game harder... because for an experienced player (i.e. one who played the game at least 3 times), the game is already too easy.
If you want, I can make a mod, which makes your soldiers invulnerable... should take about 10 minutes... but I strongly suggest to play the game as it was intended to be played.
Many people play the game with autosave only, and have no problems even on Superhuman difficulty... just look around on YouTube or Twitch, you'll find plenty of examples.