Sunday Lunch

I've always been a fan of lunchtime lunches and conversation. I especially like Sunday lunch, so we frequently ask people to come and partake food and wine with us, sitting properly at a table and having a REAL conversation.
Yesterday was no exception. Mr and Mrs Die Casting came, and Cousin Carole was still with us. We had a super lunch. As you know, I don't drink in this country, but I get quite as excited as those who do.
What did exercise our brains, though, was the present position of Miss Die Casting and her young man, referred to in her family as " German Dave".
They have been going out together for nigh on 3 years. However, the total time spent together is minimal, as German Dave works in Germany ( 5 star travelling life style) and Miss D C lives near Glasgow. GD ( whose mother is German and father Croatian) arrives late Friday night about 3 weekends a month and disappears again Sunday morning. Yesterday was no exception. Miss DC was is and continues to be extremely upset by this. There is no end in sight. Mr & Mrs DC think German Dave is a bit of a gold-digger. They admitted if he was a merchant banker earning £2million a year, living in Glasgow or London, they would not be too worried, but Mr.DC ( extremely rich) gets very defensive when German Dave's credit card won't clear.
So what to do? Clearly Miss DC moving to Germany is no solution as GD travels all week anyway. So should Mr.DC offer GD a job? But it appears GD is a bit of a rolling stone and does not want to change what he does. The real problem is the complete lack of any endgame. It'll simply go on like this forever.
The general consensus was that Mr.DC should have words with German Dave along the lines of " I'll cut her off without a penny" and see what happens.
I accept this is not up there as problems go with Darfur or Arab-Israeli conflict, but it is having a serious effect on one family.
Anyone any suggestions??