Maverick invested quite heavily in Rakhem, who as his tank against elemental enemies. He feared those investments were for nothing when he left.
The Return of Rakhem?
You will need to manage without Rakhem for a few fights, but he does return. He returns with all his equipment and skills intact. He decides the mission of the party is more important than his personal mission. It also doesn’t seem to matter if you have been aligning with or against him during the choices in Tower of Time.
So it turns out that, despite the initial scare, there isn’t much to worry about. The slightly crude but technically adept Dwarf will be at your side again soon enough. You will not even need to wait until the end of the floor before he returns to your party.