Here's how to make it so an 8 in Con isn't fatal: Give each character 3 hit dice at every level. Yes, this nearly triples their hit points. But also roll triple the dice on every damage source: swords, spells, everything. Since the Con mod isn't tripled, it won't hurt so much to have an 8.
If that's too much trouble, you could just have a game where everyone must put 10 in Con. Then they're all equal(ish) and you simply have to design the monsters and encounters to suit their slightly lower hit point totals.
As for making it something people want to max (to 20)... really the only way to do that is to make it the primary attribute for a class. Or make something really important (like to-hit, spell DC, Persuasion skill, or Paladin aura) key off of it, which is basically a way of saying the same thing. People realy don't max anything that's not a primary attribute. The main issue here is that Con is already pretty important... it really isn't fair or practical to make it a primary attribute unless you remove or severely limit its effect on hit points. Which is fine... there's no law that says Con must affect hit points.
But I wouldn't bother with all that. It's easier to just eliminate it altogether. Just let everything that used to be a Con save become a Str save. Done. And D&D remains surprisingly well-balanced with only the five abilities.
If that's too much trouble, you could just have a game where everyone must put 10 in Con. Then they're all equal(ish) and you simply have to design the monsters and encounters to suit their slightly lower hit point totals.
As for making it something people want to max (to 20)... really the only way to do that is to make it the primary attribute for a class. Or make something really important (like to-hit, spell DC, Persuasion skill, or Paladin aura) key off of it, which is basically a way of saying the same thing. People realy don't max anything that's not a primary attribute. The main issue here is that Con is already pretty important... it really isn't fair or practical to make it a primary attribute unless you remove or severely limit its effect on hit points. Which is fine... there's no law that says Con must affect hit points.
But I wouldn't bother with all that. It's easier to just eliminate it altogether. Just let everything that used to be a Con save become a Str save. Done. And D&D remains surprisingly well-balanced with only the five abilities.