Hello, first of all I want to say that nothing of this is a request for you to implement it.
I would either code this myself as an addon mod if possible, or open a PR.

I've had this idea for a specific feature and wanted you to tell me what you think about it and whether or not I should implement it as a separate addon mod or open a PR to this repo.

The core idea is waystones being able to be grouped, resulting in a set of mechanics.
A waystone group would be completely defined via datapacks.
/data/namespace/waystone/groups/groupname.json

The waystone json file would contain the following information

• Which other waystone groups would be accessible by this.
• Whether the group is accessible by non-grouped waystones
• A list of conditions which have to be fulfilled to travel to a waystone in this group
• A list of predicates to automatically assign this group to a waystone if any matches

Conditions could be anything from the players having a certain level to him carrying a specific item.
Predicates would auto-assign a waystone to a group if it was placed in a specific dimension or a specific height, etc

{
    "display_name": "The End",
    "canAccess": [
        "namespace:some_group",
        "namespace:other_group"
    ],
    "private": true,
    "conditions": [
        {
            "type": "has_item",
            "item": "minecraft:diamond",
            "negate": true
        }
    ],
    "predicates": [
        {
            "type": "dimension",
            "dimension": "minecraft:the_end"
        }
    ]
}

Use cases of this would be:

• Separate networks for separate teams of players
• Separate networks for separate dimensions
• Travel between different dimensions/places but preventing certain items to be taken from one to another

I think it'd be too complex of a system to have in the main mod, but Waystones can provide the necessary API events if you do want to write an addon mod.

As for Waystones itself, I can see native support for Team-only Waystones and dye-based Waystone Networks in the future (#279).

I agree. I think the ability to add waystones to groups/networks via an API and a handful of events would do the trick to enable to implement the rest as an addon mod