We know that after Mother Brain and Palma fell, Motavia's environment started a long tumble back to what it was in the first Phantasy Star. The solution the surviving scientists settled on was putting Wren in charge of a network that was supposed to slow the regression. It seems that is just what he did - staying on Zelan, monitoring things and not actively getting involved beyond basic maintenance.
Do you think that was the best solution to staving off the deterioration? Should they have instead continued the Daughter project? Maybe Wren could, over time, have built new installations instead of just maintaining old ones? He did have a potential army of workers, considering all the androids created or active in the various plants.