Here is an example of the problem:
A. I have an address with 100 BTC and I send 1 BTC from it to an exchange in block 708078.
You can't already use your 100 BTC address. The new fork will mark it as not valid. But you can use it in the today's blockchain.
They will use it in the today's blockchain. They will be not valid in the new fork.
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Ok, I see. You are making a new coin forked from Bitcoin.
However, your proposal to limit the amount in an address does nothing to prevent whales from selling large quantities of bitcoins.