It would be worth taking a look at
GUILD if you haven't already.
Anyway, let's approach this from a design perspective.
In a typical roguelike, permadeath fills a few important roles. Obviously, it increases the difficulty while adding risk and permanence to the player's actions, but it also preserves the game's random, unpredictable nature.
In a game that allows unlimited saving and loading, a player can equip an item or walk into an unknown room without fear. If the item turns out to be cursed or the room turns out to be deadly, then no problem! Just load the last save do things differently next time.
In a roguelike, the player is encouraged to be more cautious, since using cursed items and endangering their character can have irreversible consequences.
How these things hold up in a party-based game depends on the implementation.
How do you plan on handling parties? Will each member be allowed to have a distinct location like in GUILD or Wasteland or will they all occupy a single tile like in The Bard's Tale or Etrian Odyssey? I'll assume each character has their own tile since otherwise you can just treat the game like a normal roguelike with a locational damage system. Having a fighter incapacitated is similar to having an arm injured, having a fighter killed is like having that arm cut off, etc.
If every member has their own tile, and there is no permadeath for individual characters, the risk of scouting out unknown situations is considerably lower. Worst case scenario is your scout gets murdered and your team is now operating at 80% effectiveness in exchange for learning about an upcoming threat.
Your game can still be difficult, but the risk of any given action is reduced since even an instant death attack will only temporarily incapacitate one teammate instead of ending your game, and you'll also have much stronger options for gathering information. The end result is a less rogue-ish game. That isn't necessarily a bad thing, but it's important to be aware of.
If you do include permadeath, I think the next most important question to answer is "what now?" Is your player forced to go through the entire game at a crippling disadvantage? That could easily lead to hopeless situations where the player has not yet lost, but also has no realistic chance of winning. On the other hand, if the player can replace dead members, death becomes cheap. The player might not fear anything so long as they can arrange for one character to escape.
Again, neither of these are inherently bad so long as you're aware of the consequences. Maybe you want the player to be forced into increasingly desperate situations as their party's numbers dwindle. Maybe you want to create an X-Com-like environment where clueless recruits are fed into the meat grinder to better ensure your veterans' chances of survival.
You could also do something in between the two. The player could be permitted new recruits, but only a certain number of them. Or they could be provided an unlimited number of recruits, but each one comes with a permanent price. Maybe the player
can revive dead party members, but only a set number of times.
There are also hybrid options to explore, such as giving the player an opportunity to rescue incapacitated party members, and only permanently killing them if the player fails to do so.
There's a lot you can do with the idea. It all depends on what game you want to make.
Poll