Perhaps the more interesting part of the question posed in the OP is, say if Lee became incapacitated for field command in '64, who he would have recommended as his replacement to lead the AoNV at this time (remembering his presumed likely nominee, Longstreet, was grievously wounded on May 6, and would take months to recover).
Given Lee's known observance of the rules and regulations, especially relating to the chain of command, this may not have been an easy selection. Apart from Longstreet, his other permanent corps commanders at the time were Ewell and A. P. Hill. But Ewell was feeble and on the way out and Hill's fluctuating health made him unreliable. And there did not appear to be any other capable senior generals available that he could have pulled from other theaters.
So thought Lee's recommendation for army leadership might have been a dark-horse nominee from the levels of divisional command in the AoNV (after appointing him to permanent L-G rank) - maybe Richard Anderson.
There were very limited, if any, real options here for Lee. It would have been a difficult choice for him in these circumstances.