In my (German) company we get to keep the miles/points for our private use (flights/hotels). However we regularly (read: always) leave for our trips on Sundays and arrive back on Saturdays.
Basically it is a mutual understanding if the company would keep the miles we would start travelling weekdays. That would mean instaed of 5 full working days at the destination we would only have three (TUE-THU) as we would travel on MON and FRI.
In my opinion that is a win-win situation and workable for all involved.