The great thing about crypto, if you use it correctly and don't rely on centralized exchanges, is it's trustless. I literally have no way of taking your funds. Your coins never leave your wallet. Before you interact with the kyber network smart contract you can review and sign the transaction from your metamask wallet.
If I understand this question correctly, tokenfolio.cc does this already. It looks at your old portfolio allocation and your new portfolio allocation and performs the minimum amount of trades to the kyber network to facilitate the order.
This product will only rely on DEXES for the backend and never connect to a centralized exchange.
It depends on how you define expensive, if you look at the whole picture it could be more expensive to use binance.
1. To move coins to binance you have to send coins (transaction fee) and then wait for confirmations
2. make trades (taker/maker fees)
3. remove the coins back to your wallet (binance withdrawal fees)
With the kybernetwork you sign the transaction from your wallet, pay gas fees (that you can choose) and your new coins appear in your wallet.
By using a dex you gain not only convenience, possibly even lower fees, and security as well (exchange can't run off with your coins or get hacked)
Thank you for the feedback! It's very helpful for me so I can see what users want.