1 minute ago, Budgernaut said:He could, but the opponent chooses the figure to suffer the damage, so your opponent is unlikely to choose the Geomancer until it is the only
unitfigure remaining. (See Damage, 22.1 in the rules reference).
The larger problem is that the upgrade can only be put into a block of 4 trays or more, so you're gonna hurt yourself a lot before you get to that point.