I agree Bingley himself would be an ideal husband for a shy young woman and Darcy would probably like to encourage Georgiana to marry a family friend for reasons you mentioned. Yet I believe he would have doubts about bringing Georgiana into Caroline's orbit of influence. For instance, (Ch.10); Darcy is writing to his sister, Caroline asks Darcy to 'tell your sister I long to see her.' Darcy replies 'I have told her so once, by your desire'. I interpret that to mean Darcy wouldn't normally mention Caroline Bingley in a letter to his sister, certainly not twice! He would not encourage a friendship between them. As for Darcy's dislike of Caroline, I think this is demonstrated in Ch.6 when Lizzy declines to dance with Darcy and Caroline comes upon him with the comment he must be considering 'how insupportable it would be to pass many evenings in this manner-in such society; and indeed I am of your opinion...' He contidicts her with the remark 'I have been mediating on the very great pleasure which a pair of fine eyes in the face of a pretty woman can bestow' His reply astonishes her. I wonder if it was because she expected him to say her eyes or because it was Eliza Bennet? (In P&P2 in this scene Anna Chancellor does a great eye rolling act!) I know Caroline likes to imply she is intimate with Darcy yet she hardly understands him. He is far more complex than she realizes. Generally, Darcy only speaks to her when she speaks to him first and tolerates her presence at best for Charles'sake...Now if Caroline were to make a grand marriage that meant her residing most of her time in the Scottish Highlands or Cornwall, I wonder if that would throw a different light on it? ;)