I don't believe you can do this with MacOTP, however I think you probably could (I haven't tried, just speculating) if you wrote a custom AAC policy that managed the OTP portion yourself and leveraged your own instance of the "Email Message" mechanism. On the Mechanisms panel you can create a new "Email message" mechanism, just like you create an Infomap. A preceeding infomap would setup all the email message that you wanted to send. You'd obviously then also have to write a subsequent Infomap that prompted for and validated the OTP. A little bit more involved than using the OOTB MacOTP policy, but I think this will give you the flexibility you are looking for.