If Regions was willing, I would not be surprised to see BB&T buy Morgan Keegan offices, to merge into their Scott & Stringfellow sub, in order to fill in gaps in the S&S coverage of the BB&T footprint. Hoewever, I would not expect Regions to sell pieces and parts.
The Capital Markets effort at BB&T is a loss leader at worst; at best its simply a low margin business (when it is supposed to be a high margin business) for shareholders. The only thing they need from MK is to buy the brokers, nothing else has any value. But as any good broker will tell you, he will jump ship for a price, so such an acquisition would be a wasting asset. Also, BB&T last year lost the guts of its Bond desk, which was the only thing that made its Capital Markets sub any money at all.
I would suspect that at BB&T, they are saying "Gee, we should sell off our capital markets group too, let's wait and see how much Regions gets for MK." Or better, somebody buys MK and then at the same time buys out BB&T's shop.