• More convenient C++ BSON builder syntax
• Maybe a fast field lookup operator[]
• Maybe cursor::foreach
• Maybe a nicer way to iterate over bson elements. Right now, to iterate over a nested document or array, it's necessary to call get_document()/get_array():

for (auto&& element : doc["subarray"].get_array().value) {}

It should be possible to return an array or document iterator immediately, depending on the type of the element.

for (auto&& element : doc["subarray"]) {}

Ideas courtesy of ryan.timmons:

• Maybe a bson_doc["item"].to_json() rather than to_json(bson_doc["item"]). A static method bsoncxx::document.from_json() would complement this nicely.
• Better document best practices for usage of views/values/value_or_views, since this seems to be a common point of confusion.
• Maybe a better way to go from a bson type to a native type, e.g. bson_val.as<int>()