Can I keep Cash on Delivery but force prepayment for risky-looking orders?

Yes. Use Orders → Fraud Protection:

1. Make sure Enable risk scoring is ticked.
2. Under Auto-action policy, set High-risk orders to Block COD at checkout (force prepaid).
3. Click Save settings.

Orders that score High risk then can't be placed with COD, so the shopper has to choose an online method. Everyone else can still pick COD.

You decide what counts as risky with the Rules (for example COD return history (RTO) or Blocklist) and the High score threshold on the same page.