I was wondering recently if I could even take it a step further and grant max HP instead of average when levelling up (as in 1st level). Obviously this means tougher PCs, but then I can always be more mean with monsters if I feel the encounters are too easy. Mainly, the effect would be to make the players less worried about dying in the first encounter of the day or from a single unfortunate trap/attack/spell.
And one question - are you trying to prevent characters from dying, or "make the players less worried about dying". Because 5e already has a nice thick buffer between player fear of character death, and actual character death.
If none of the PCs have died yet, is their fear unfounded? Maybe allow an extra death save if they are more concerned with dying than just going to 0 HP?For the record, it's about worrying, because I haven't actually killed a PC yet.
No tombstones yet? Nice. I had a TPK the second season in 5e lol.For the record, it's about worrying, because I haven't actually killed a PC yet.
If none of the PCs have died yet, is their fear unfounded?
You can also allow certain "bosses" to Second Wind once or twice for health bars.Giving NPC an uncanny Dodge like feature works well. Boost in survivability without just making it a HP grind.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.