If you want improvements built on the current engine, I'm afraid I can't help you. I can't even fathom how the designers intended stealth to work. Interesting thought experiment: WotC releases a set of examples, a youtube video or something, that clearly and uneqivocally sets down the parameters for which the different stealth components work and how they interact with each other.
Yeah, I don't see that happening either. What does WotC stand to gain? By pleasing one third of the customer base, they will alienate another third, with the third third not even caring.
So my best advice is to look at your favorite not-5E game for a stealth system that works for you. This could be a previous D&D game; it could be some completely different game (like Runequest or WEG Star Wars).
I've not once had a problem at the table running stealth.
Came up five times in the last two game sessions I've run:
1) 8th level PCs sneaking up on an armed camp to scout and free a giant imprisoned in a large cave at the back of the camp. Ranger and Cleric want to sneak up edge of the front of the camp. The ranger casts
pass without trace so they both get a +10. The rogue and dex fighter sneak to the back of the camp. Everyone makes stealth check vs passive perception of guards. The all succeeded. Next the rogue needed to move up to the giant to try to free it. But this required crossing some open ground. So stealth vs passive perception with adv (+5). She succeeded, freed the giant by picking the locks them moved away (another stealth check vs pp w/ advantage).
2) After freeing the giant (and telling him to remain still until a fight started) the rogue and fighter (being the high CHA characters in the party) walked into the camp and attempted to negotiate for the giant's release. When this failed, the ranger and cleric snuck up to the edge of the camp (vs pp w/ adv) and attacked, gaining surprise. The rogue and fighter I allowed to make a deception check vs insight to not give away the ambush. They succeeded so I gave them advantage on init but treated them as if they were surprised in regards to how initiative played out in the combat. The rogue made a ranged attack, moved behind a tent and hid. Next round she emerged to make a ranged attack (at adv from hiding) then hid again. She wanted to hide then move up to attack with advantage but I ruled her target was too aware of her and the ground was too open so she could not do that. So instead she chose to move up, attack and then dodge.
In another group w/ 12th level PCs in Castle Ravenloft:
3 ) A group of 7 Barovian witches were aware of the party entering their lair (the party had the witches' hag's eye). So 3 of them cast invisibility and hid. One witch cast alter self to look like a non-threatening woman who would distract the party and try to negotiate to get the eye back (and 3 others precast spells outside the room). The first PC into the room was looking for threats so she got an active perception check at disadvantage (effectively blinded). The other PC that entered the room just used passive perception w/ disadv. They noticed the threat (witches are bad at sneaking) and combat ensued from initiative which everyone rolled normally. The PCs could attack the invisible witches w/ disadv and the witches could attack with adv.
4) As the party was entering a tower via a bridge a battle started with animated weapons inside the tower. Vampire spawn were crawling up the tower under the bridge out of sight. I rolled stealth vs. passive perception of the two characters in back (standing on the bridge). The vampires got to attack w/ adv against the one PC that failed to notice them.
5) Once the vampires had swarmed onto the bridge the warlock flew away and the shadow monk used darkness then jumped off the bridge. The warlock had devil's sight so he could pummel the vampires with advantage. The paladin remained on the bridge in the darkness. He could attack the vampires normally and the vampires could attack him normally (both the vampires and the paladin were effectively blinded). He had used oath of enmity against one vampire prior to darkness being used so that vampire he could attack with adv. The wizard could not fireball the bridge without hitting the paladin because he could not see into the darkness to avoid hitting his ally. Eventually two vampires jumped down and killed the monk (killed, dead, won't be down for breakfast) ending the darkness spell. The paladin went down before he could revivify her but since he was not dead and now the wizard could see, the wizard cast polymorph on the paladin, turning him into a giant gorilla...epic gorilla vs vampire swarm hilarity ensued....
My players were satisfied with every ruling, each situation was exciting and memorable and involved a risk of failure and a possibility of success. The stealth rules (or at least my interpretation and application of them) performed as desired. IMO, the vagueness in the system is by design to allow a DM to make rulings on the fly that make sense for the current situation quickly without getting overly bogged down in looking up rules or trying to figure out how to apply them to complex and changing situations. "I hide" "Make a stealth check w/ adv/disadv vs perception w/ adv/disav" is all you really need to ever worry about. Sometimes the DM can rule that hiding is simply impossible (but this should be relatively rare, IMO).
