In the midst of a merger and federal investigations, Naples-based hospital chain Health Management Associates late Tuesday said it would propose a concession to a major shareholder that has sought to replace the corporate board. But the shareholder, Glenview Capital Management, quickly rejected the offer Wednesday. HMA said Tuesday night that it would be willing to add nominees offered by Glenview to the board and was prepared for one of Glenview's nominees to become chairman. The proposal came about a week after the announcement that Tennessee-based Community Health Systems Inc. intends to buy HMA in a $7.6 billion deal.