Simply make all campfires the only item to allow short and long rests ; there are campfires is coherent spots along the road, have players to reach those locations to be able to short and long rest.
- Use campfires for short rests, this way you can have maybe interaction (and story progress) with your party companions only while you're adventuring with them.
- If you want a real long rest, allow them only to occur in either one specific location (at center of the world map for instance) like we had in BG2 with the old castle (wich could be improved and held all your side companions, gear, merchants, crafting stations etc), OR use localized "big camps" where we have to travel, and where we should see all our companions, merchants and storage.
- Clearing big zones out of enemies could create a "safe spot" where now you can long rest safely until the end of the adventure (like the castle in BG2). You may even find "little campfires" guarded with enemies that you have to clear first before using short rest here.
This way you'll have a sense of logic ; you can use this little 'safe' spot to short rest (around 4h) even in not entirely safe areas like underdark, but to take a full rest you'll need to physically get to a safer encampment, one that you cleared/discovered beforehand.
- About fast travel, it should only be available by physically using a rune (ie. going to a rune location), not from anywhere in the world since it looks silly/too easy.
By those adjustements I think players will get choices, by discovering "waypoints", either being abandoned campfires, occupied ones, or runes of fast travel, wich should give many options to how they want to play their quest. Do they want to travel with same companions all the way, only resting by short periods and only talking to them, or backing to the last big safe zone to spend the night with all of them, at the cost of a less steady progression...
And players will have a bit more of pressure, in the way they wont have access to an immediate campfire, and may want to be more careful with ressources (consumables and spell slots), knowing they will not be able to refill everyone as will in every situation, but they will always get the options to get back to latest waypoint (being rune of fast travel or campfire) to resplenish ressources before venturing forth.
Or you can just use the system from BG2. I think this is the best compromise.
