As long as both players are agreeable then the casino is unlikely to stop you. In some situations it may not be practial because the player may want to take more than 3 cards. However with 10 against 4 the player should never take a fourth card, thus it was a good idea. Although a bit impractical you could always offer to buy the player’s hand and then you play it yourself, if you can agree on a price. My blackjack appendix 9 shows the fair value of all hands. As an example suppose another player had blackjack and the dealer had an ace up. Most players would take even money. You could make money by offering that player more than even money, but less than 103.8%, and then playing out the hand yourself. However don’t extend this offer to a card counter.