This is true if you design the rubber band in a poor way. In the extreme, you could give a player leading with one goal a 50% pace handicap. Nevertheless, as also mentioned earlier, bad consequences like this can be avoided by designing the rubber band with more care.
Of course for now we are just theorizing and the question is which parameters would be the best to influence. Mr. Bishop said, I believe, it should include (or use solely) the ability of the keeper. Or the quality of the shots maybe. But possibly, only affecting the pace won't help much (except forcing more lobs from the player ahead?).
As I argued before, the combination of a buffer and rubber band won't help anybody to upset a stronger player. Depending on the implementation it would just reduce the scores slightly. So it brings me to the point: What exactly should the purpose of this be? In your first post, Dagh, you said it is to help the weaker players. And it's a nice idea. The problem is that it might be impossible to find an implementation which could also be used for all other matches without negative side effects. Maybe we would have to open up the can of worms you'd like to keep sealed.
Yes, you bring up a good point, that some tournaments are more suited for this than others. I think I would like to adjust my statement. Yes, you can have one pre-tournament measurement: Should we use this handicap feature or not? Since some tournaments are more suited for this than others, and this depends on a pre-tournament measurement.
This would be the easiest solution. I can totally see that for some tournaments this would be very useful. The idea came to you when you where thinking of the next Scandinavian Championships which could end up with you and John winning many games by a huge margin and not be much fun, especially for the poor guys on the losing end. Any variation of your idea might make the tournament a lot more fun. Nonetheless - will you turn it off when facing John? And what if two weaker players of roughly the same level meet?
If you use a buffer and rubber band it just won't help the weaker players enough and the games will remain one-sided for most of the match. If you leave out the buffer then you'd be keeping games between similarly strong opponents artificially close. So I cannot - for now - see it being used in general, it would actually need to be decided based on individual players. In this example, maybe you and John could agree beforehand on which players both of you turn on the handicap feature for.