The only way someone can "intercept" is if when BTC moves from wallet, the pubkey will be exposed, and someone with kangaroo can quickly find the priv key. But many people have said to use electrum(?) and to uncheck the replace by fee option.
In this situation; Once someone finds the private key, won't they be able to transfer the money to another wallet? Is it possible to transfer money instantly by paying a high fee?
Unless you brute-force and broadcast fast enough to win the "race condition", most likely it'll fail. Node will reject your transaction since it's conflicted with transaction which already exist on node's mempool.
If you're pool owner, you might able to include the "malicious" transaction on mined block, but i've no idea whether it's actually possible on reality.