I also could wish (eboulomhn kai auto). The imperfect for courtesy, rather than the blunt boulomai, I wish, I want. Literally, "I myself also was wishing" (while you were talking), a compliment to the interesting story told by Festus. The use of an with the imperfect would really mean that he does not wish (a conclusion of the second class condition, determined as unfulfilled). An with the optative would show only a languid desire. The imperfect is keen enough and yet polite enough to leave the decision with Festus if inconvenient for any reason (Robertson, Grammar, pp. 885-7). Agrippa may have heard much about Christianity.