Grittier play. More thoughtful decision-making from players who take the current system for granted. Most players don’t really think there’s much of a chance that their character can perish in 5e.
Re: #1
Ok, and you're aware that this is going to specifically target anyone who plays a melee or tank, because as an experienced DM, you're well aware that death saves are
absolutely not evenly distributed throughout the party?
So you specifically want the players who play to tanks and melees to "feel the grit", but not the players who play other classes?
The reason 90% of "make it grittier" stuff focuses on HP regen is that all classes lose HP, but not all classes end up making lots of death saves.
Also, are you talking three failed, or three rolls at all? These are very different scenarios. Three rolls at all means you're going to get 5MWD syndrome if your players value their PCs, because no-one in their right mind would continue after even making one death save. Three failed has a bit more flexibility, because players are willing to gamble with RNG, but not so dumb they'll mess with a sure thing.
If your problem is solely overconfident melees get whackamole'd, then go ahead (though I'd say failed rather than all). Also be aware that this will be "solved" at level 5 when Revivify kicks in. If you feel like it's not just melees, or you don't want to single them out and punish them for playing those classes/specs, then drop this and go with something that makes it harder to regain HP (very much including HP from magic).
Re: #2
This is also going to impact melees and tanks far more than others. They're up front and will catch far more in the way of touches, won't they? So you'll have the Fighter, Barbarian, Paladin and Rogue limping around on various levels of Exhaustion, whilst the Wizard, Sorcerer, etc. stand smugly at the back with none - and who also aren't having to worry about death saves much (I've literally never seen either class have to make 3 death saves before a long rest).
However, with the restoration changes this isn't killer and I honestly think they should have used Exhaustion in a lot of cases with these monsters.
Based on what I can see, you're likely to experience more in-combat healing, spare the dying (which basically means a player is "out" until they receive healing), and long resting to get rid of exhaustion. You might see some more cautious play, but it's likely to be centered around healing and resting than anything else. I would say make sure you include time pressure in your games else they'll just long rest as much as they can. Make it a meaningful choice with trade-offs, I say.
Exactly right. And if you just time pressure them and do this, in the long run the only PCs will die will be ones who play melees and tanks, and that's likely to mean your players just move away from playing those, rather than being "cautious". Caution is hard in a game as RNG-heavy and DM-strategy-dependent as D&D - particularly as an awful lot of caution relies on casters buffing/protecting the people up front, and they're not the ones who will be suffering here.