When syncing for the first time with Booking.com, do not allow if currency different to the one that is used where the property is.
Priced in USD for a property in Thailand. Booking.com showed in Thai Baht. It was only a couple of hours before I realized what happened, and someone booked the placed at a ridiculous low price. Will lose money with this booking.
I know my mistake. Would be good if this was really made clear and really should be not allowed.
This brings up the second feature request.
The best would be to allow rates for the same property to be in different currencies. Offering in this case to create these new rates, based on the exchange rate.