When block 100,000 is mined, drop the oldest 50,000 blocks. The remaining oldest block is the new "genesis block". Any remaining unspent outputs on the dropped blocks are given to the miner.
Bam, done.
This is a horrible idea.
Thankfully it can't be implemented without consensus from all of the users of bitcoin, and I'm confident that you'll never be able to get consensus on such a poor proposal.
Yep, it's a pretty bad idea for Bitcoin.
Do you mean it couldn't get consensus to make that change among users, because I totally agree with that, or do you mean that the blockchain couldn't get consensus with a sliding history like this, because I don't agree with that (For the most part.).