This doesn’t require any structural change, just a procedural one.
Contesting parties and independents each publish a policy prior to an election at any level.
Each candidate enters into a legally-binding contract with their electorate to uphold the policy they subscribe to, whether party or individual.
If it’s a party policy, then each party-endorsed candidate is jointly and severally bound by the contract, with both civil and criminal sanctions as a consequence of the breach of contract.
As to the civil remedy, a penalty of a forfeiture equal to the deposit of each candidate and the assets of the party. As to the criminal sanction, a wilful breach of the contract will constitute at law as electoral fraud.
Want honest politicians willing to keep their word? Here’s a start.