It makes it much easier. More nodes will accept the mutated transaction then would accept a transaction that outright conflicts with an existing transaction in it's mempool so the chances of getting the mutated transaction confirmed are greater.
If you make a first transaction will be first to yourself and after immadiatly you will pay to other who accept 0-confirmed tx - yes, this can help to you if your first tx will be duplicated by attacker firstly and be accepted by miners. Ok. But it's difficult way. Ok, you are right, may be it will help.