I have no idea of the physics of this. So, a genuine question; is an extra 0.2 degrees likely to make an appreciable difference ?
If the speed control was up to the pilot the 0.2 deg. wouldn't be an issue. At LHR the ATC puts you under strict speed control to achieve separation, e.g. 160 kts to DME 4. The idea that you can't go down and slow down is very true here.
Relating to my type, a solution would be to configure (extend gear and flaps) early. Now, due to excess drag, I would have to fly with partial thrust on which would negate the noise benefits.
The problem, as I see it, is not the glide slope angle. It's the glide slope angle with tight speed requirements and the current flying technique of keeping the aircraft in a low drag configuration as long as possible.