We have released new update for WooCommerce Simple Auctions v3.0 with two new features you asked for: allow bids if user has stored credit card and auto charge for won auctions if user has stored credit card. These new features work with WooCommerce Stripe Payment gateway.
First one allows users which have valid payment option saved (credit card) to place bids. This way you can verify user’s payment method.
Second feature allows to automatically charge saved card in case user has won auction. Order is automatically created and saved credit card is charged.
New version is published on CodeCanyon. If you have questions feel free to open support ticket.
