This isn't quite as impossible as you make it sound. You can certainly make it feel like you have this behaviour by triggering A on release if the button is held for < ~300ms, or whatever feels right as a short press.
Of course now you have to accept the button doing nothing if it's held for longer than 300ms but shorter than 3s, but making it slowly fill up with another colour or something is probably enough to communicate the long press behaviour.
Of course now you have to accept the button doing nothing if it's held for longer than 300ms but shorter than 3s, but making it slowly fill up with another colour or something is probably enough to communicate the long press behaviour.