The luggage problem exists on Finnair and is on the rise.

But priority boarding is also about getting to your seat and escapning the boarding chaos. I prefer to wait for take-off sitting in my seat rather than standing in the gate area. This can easily be arranged even with bus boarding and many airlines do.

What can't be accommodated at a busgate is the "board at your own convinience", ie a priority lane that allows you to skip a line if arriving late to the gate.
I think QR does drive one early and one late J-bus to the plane, but unless you are the last J pax to arrive, you still will be waiting on the bus before boarding.