I think that an AI can only U-Stamp a vessel to the latest code at the time that the Purchase order was placed. Perhaps someone would correct me.
Therefore, your only option is to U-Stamp to the latest code.
If additionally, the customer wants compliance with 2017, then include any extra NDT and print off the 2017 calcs and charge them for the extra design work. But all that extra work won't have anything to do with the U-Stamp. It is just a customer requested extra.