Flat tax + basic income is the only sane way forward. Most other systems lead to stupid incentives, unjust inequality, and over priced accountants.
For example. Assume a household of two people. one earns $20k per year, the other earns $80k per year. With a 50% tax and a $10k (after tax) per year basic income you get the following:
2*$10k + 0.5 * ($20k + $80k) = $70k
Now if each partner earned the same you would get:
2*$10k + 0.5 * ($50k + $50k) = $70k
Which is exactly what you want. The problem with income splitting measure that try to replicate this is that they lead to a perverse disincentive to divorce. So in the first example, the person earning $80k would no longer be able to offload part of his income to the lower paying person, and the two persons effective income decreases just when their expenses double. Furthermore it discriminates against people that are single, which is politically expedient, but unjust.
It also solves the welfare and old age security paperwork problem. There are some other problems: like having a higher tax rate to pay for all this basic income, but ultimately I think it would unleash more minds on problems that matter instead of setting up family trusts for the wealthy.