Social support for the elderly vs. social support for the infirm

In recent days I've had cause to spend some time on the WINZ website.  Whilst there, I was confronted with something I've been shocked by before:

1. A married couple who both have health conditions that render them permanently unable to work, but who happen to be under the age of 65, will be given $558.26 to live on by the government;
2. A married couple who are fit and healthy but happen to be aged 65 or older, will be given $638.46 per week to live on.

Around $80 a week is a big difference.

If the older couple have health problems of their own, the discrepancy becomes greater:

1. A married couple who both have health conditions that render them permanently unable to work, but who happen to be under the age of 65, will be given $558.26 to live on;
2. A married couple who both have health conditions that render them permanently incapacitated, but who happen to be aged 65 or over, will be given up to $761.22 to live on.

Around $200 a week is a huge difference!

Similarly, if the two couples needed assistance with housing costs, the help offered to the older couple would be a lot more generous than that offered to the infirm couple.

The data I'm working from is all on this pdf.

Note that benefits for people with permanent health conditions are known as "Supported Living Payments" these days, not Invalids Benefits).

This seems to me blatantly unjust.  I'm OK with the unemployment benefit (known these days as "Jobseeker Support") being at a lower rate than Superannuation: you're not expected to be unemployed for the rest of your life so it's not so important that it's at a long-term liveable rate.  But I'm not OK with those who are unable to work being treated worse than those who are simply old.  After all, the only reason we give financial support to older people is because we consider them too old to be able to work!

What would I like to see done?

I'd like these Superannuation and Supported Living Payments to be set at the same level.  People who won't be able to work again for the rest of their lives and people who are too old to work again have the same needs and so should receive the same support.  I don't hugely mind which level the two benefits are set at (i.e. at the current rate of Super, the current rate of the Supported Living Allowance or somewhere in between), but I strongly feel the rate should be the same.

If it's considered politically impossible to lower the rate of Super then this proposal would increase the government's costs.  In that case, I'd propose raising the age of entitlement to Super to 70 (in order to make the change fiscally neutral) but with one proviso.  Anyone aged between 65 and 70 who was assessed as unfit to work due to their physical or mental health, and who is assessed as being likely to stay that way for at least 6 months, would receive a Supported Living Payment.  Once assessed as eligible, they would remain eligible until they turned 70, without periodic reviews.  This would mean that, in effect, between the ages of 65 and 70 Super would be needs-assessed, and from the age of 70 it would be a universal entitlement.

Why?  With increasing life expectancies, many people are staying healthy and able to work well past 65.  It makes sense to me to increase the age at which we say that you are probably no longer fit to work in order to give money to those who have actually been assessed unfit to work.  However, some people (e.g. people who've done physical work like shearing or people who just have bad genes) get 'old' at a much younger age.  It seems harsh to force those people to either continue trying to work or to perpetually prove their incapacity once they've demonstrated their working days are done.  Not requiring regular reviews would also save money, and I doubt it would result in many people fraudulently receiving this special Supported Living Allowance at any time as you could only receive it for a maximum of 5 years anyway.

If life expectancy continues to increase, I'd want to periodically increase the cut-offs for eligibility both for Super and for this special Supported Living Allowance.

I'm not sure what to do with my idea.  Does anyone know?  I know that John Key has emphatically stated that he's not going to increase the age of entitlement to Super so long as he's Prime Minister, plus his government has really tightened up entitlement to other benefits, so it's probably not worth talking to him.  I guess that means I should try and lobby Labour or the Greens, but I don't know how to go about getting their attention on an issue that's not one of current debate.  Any ideas (or any feedback on my solution to the current unjust system) would be appreciated!