Is your half year at DTW going to be one time only or an ongoing thing? Will you be flying within North America during the half year(s)? I'm asking because it might make sense to pursue status with DL which could give you a dew domestic FC upgrades and certainly some preferred and C+ (extra legroom with a few extras) seats. If you maintain an address in France you would be exempt from DL's MQD (spend) requirements for status.