what I would like to see sorted is the situation that screws me and the wife over
we both work full time but I earn 3x what she does
why is it right that we pay lots more tax than another couple on the same total but a 50/50 split of income?
Because you aren't taxed as a couple.
A balancing like you are suggesting means there is a massive tax break from simply being married. I would be very strongly against that.
Take the extreme (although not uncommon) example of a single earner, and a single earner who is married where the partner earns nothing or very little.