One of the major purpose of out-of-zones Contactless ticket payment is to protect revenue for train operating companies outside TfL (and this is basically the ticketing requirements when Elizabeth line extends West) so I’m afraid you can only split your fares by touching in and out at West Drayton no matter you hold a paper ticket or not between Maidenhead and West Drayton.
However, I don’t think you need two bank cards to split your journey at West Drayton unless you need to tap back in within 2 minute time out time.