That works pretty well. It does mean that Vampires will have a very hard time turning commoners, but that is not necessarily a bad thing.
Right, and here's a few more details:
Vampires in my games don't want more vampires. Making another true vampire, even an underling is a threat to both them and other vampires. Like classic Dracula or Strahd, it only happens when a vampire has a particular obsession with a person and wants an eternal companion. Vampires have no problem raising the dead and can raise any creature they killed (at any point in time) as an undead ghoul/skeleton/other lesser undead depending on body decomposition as an Action. Vampires want cattle, thralls, slaves and other forms of underlings. Not equals.
NPCs rise, or don't rise as a new vampire based on, above all else, DM discretion, secondly on a "will to live" save. If their will to live is stronger than the vampire's will to not make new vampires(DC 12 for rogue vampires who don't care, 15 for vampires who are indifferent and 18 for vampires who actively oppose), they have a 1/4 chance (4 on a 1d4) to rise as a vampire
after 3 days. It may take longer, it may not, but it is a minimum wait of 3. The latter rules apply to players as well. Get killed by a vampire? Make a CHA save. Succeed? Roll 1d4. On a 4, congrats you're a vampire! On anything else, you're dead. This process cam be prevented of course by various, rather barbaric methods of mutilating the body, like removing the heart or head.
And since vampire turning remains largely in the hands of the DM, it keeps players from getting silly with it.
This I like. I do miss con damage, then again I am using the vitality rule from the UA and a strong believer 5e holds hands a Tad to tight
My players are pretty strong optimizers, so I've had to get creative to get around their defenses. I've found that direct damage to their stats has a much bigger impact on how they play and how they react than HP damage. Which makes sense, stats cap at 20, they're a limited commodity. HP doesn't. I'm basically using all these little experiments in my current game to figure out how to put the appropriate horror into a Ravenloft game.