Unique Entity Types in an Archetype-based ECS

Question

I am currently designing an Entity Component System (ECS) where each entity is of a unique type:

template <typename... ComponentTypes>
struct Entity
{
    using Signature = std::tuple<ComponentTypes...>;
    size_t ID;
};

This design decision has led to some unique challenges and I'm seeking advice on how to handle them.

1. Non-contiguous Entity Storage: The main pitfall for me is that it's harder for the user to store the entities contiguously, because they would need a container for each component type variation.
2. Order-Independent Component Types: The order of the Component types doesn't matter. For example, component types: ["Position", "Health"] is the same as ["Health", "Position"]. You can find the essence of how I did it here: Link. I am basically sorting the types at compile-time.
3. Archetype-Based Design: I'm using an archetype-based design. I am using a type-erased archetype object, which I need to cast to the respective type to access the components. Each archetype stores a sparse set of Entities, along with a tuple of vectors for the components.
4. Accessing Archetypes: To access an archetype, you need to know the whole list of types the archetype stores. This is the main reason for the templated Entity.
5. Strongly Typed Systems: Systems are strongly typed at compile time, which is similar to how ECST does it.
6. Entity Type Change: Each time I add/remove a component, I need to change the type of the entity.
7. Entity::Signature as Key: The Entity::Signature acts as a key to know in which Archetype type the Entity resides, which would be faster than looping over all the Entities and checking if the IDs are equal.
8. Heavy Template Metaprogramming: I am heavily relying on template metaprogramming. This provides type safety, as the compiler checks that the types used with a template are valid for the operations the template performs.

I am interested in hearing your thoughts on this design decision and any potential pitfalls or improvements you might suggest. Thank you in advance for your insights!