Some of the proposals for the $12.6 million Liberty Bell Center include exhibit materials related to slavery and freedom in early America.
Designers also have suggested a commemoration for the eight slaves that George Washington owned during his presidency in the 1790s.
National Park Service officials say the proposals, presented at a recent meeting, are only ideas. They plan a public meeting on the issues this month.
Some people were angry when it was reported that the pavilion's entrance would sit over the site of Washington's slave quarters during his presidency.
The Park Service had no plans to mention Washington's slaves in exhibits or to explore the broader issue of slavery in colonial America. After a public outcry, designers were sent back to the drawing boards.
Park designers also are considering how best to commemorate the President's House itself, which was near Sixth and Market streets. Washington and the anti-slavery John Adams lived there during their successive presidencies.
Designers are considering a ground outline of the house's footprint, according to some who attended the closed meeting.
Edward Lawler Jr., an independent scholar who attended the meeting, said he believes slavery will be a major part of the design.
"The President's House will become a major site for African-American history, as well as American history, if what was heard (at the meeting) goes through," Lawler said. "It's such a change."