If only the two of them could figuratively combine with each other. Ling Xiao would provide his skills and intelligence while the other successor candidate would contribute his heartless and ruthless personality, mixing the both of them would create the greatest marshal the Federation had yet to see.
Even with all the positives of Ling Xiao, the First Marshal logically still felt that the other successor candidate was more suitable to inherit his throne. But, if he took his emotions into account, he wished that Ling Xiao would take over his position. After all of his deliberation, the First Marshal decided to give Ling Xiao another chance.
The First Marshal believed that Ling Xiao was clearly aware of the trap. If he would make the right decision as the commander-in-chief, the First Marshal would have a reason to push Ling Xiao to a higher position when he returned.