I would like to recomend 2 features one is more a convenience one and i know that sfml is not intended for convenience features but I still think it should be implemented.
1) being able to use math between a sf::Vector and a single number(a int or float etc) with operator overloading something like
sf::Vector2f position(2,4);
position += 1;
position *= 2;
and that position would equal 6,10 most vectors of other programs and libraries have this functionality
2) being able to get the type of keyboard (azerty, qwerty) being on a azerty myself this would help, so for example automaticaly detact the keyboard type and adjust the key bindings acordingly like wasd keys most of the time are wrong on azerty's
thank you for reading :)