Society has various ways to solve this problem, and one of those is inheritance tax.
At least over here in The Netherlands, the inheritance tax is money you pay when someone else dies, and you get their money/assets. The justification for having these taxes as far as I can find it, is that it's meant to prevent people from mooching off of other people's work/money. Yet I somehow doubt inheritance tax money over here is actually redistributed and that our government is some kind of good-hearted Robin Hood stealing from the rich and giving it to the poor.
Long rant against inheritance taxes short: inheritance tax is not society's way to solve this problem. You're (presumabely) not dead, and there's been no transfer of your contributions here: No one else is profiting of your original contributions in a way that would require them paying an inheritance tax. There's also no need for redistributing reputation points.
But I wonder how fair this is to people starting on the platform today.
Besides unlocking some site functionality (privileges), a reputation point doesn't have any value that can or needs to be 'taxed', so that newer users can still have their reputation points too. There's no finite amount of reputation points that needs to be fairly distributed across users, it's not like any site here is running out of reputation points faster than reputation points can be grown or created.
What's fair is that you wrote some good posts in the past, and that people are still thinking those deserve a reward. What's fair is that there's an unlimited pool of reputation points for people starting on the platform today, and they can earn as many as you.
Perhaps the only thing that's 'unfair' is that you had years of head-start on those that start on the network today, but that would only be unfair if there was an end-goal, a finish line. There are no finish lines on SE, so I'm going to say that anyone that compares their 10 minute old account to one that's 8 years older and expects the same numbers should probably have a lesson in interpreting and comparing numbers.
leave these accounts with roughly the same amount of reputation they gained whilst being active.
There's another point here that's tricky: You assume that just because someone isn't posting, they're not active, and shouldn't be gaining reputation anymore. But these people can still be active, just in other ways: Closing posts, deleting posts, editing posts, flagging posts, and voting on posts. Seeing people still benefit from my older posts while I'm busy doing all these other things is nice.
Upvoting or bounties are a much better way of raising new users up then just taxing existing reputation away into a black hole. Vote early, vote often lists three main benefits of voting: good content is voted to the top, wrong or incorrect content is voted to the bottom, and users who consistently provide useful content accrue reputation and are granted more privileges on the site. Especially that last one just can't be achieved by siphoning away reputation from accounts.