I can understand, that it might look strange sometimes. But having the planes holding on the taxiway instead of the runway ramp, means that no plane can cross behind. At my airport, where I use staggered depatures that would mean, that I could not have two planes (LArge and Medium for exmaple) in the “ready-position” at the same time.
Please consider it´s a game after all, and as long as the map size is quite limited, it would be very challenging to fit everything to spend even more space for the taxi/departure infrastructure.