The Mother Worm, beyond its primary unit, seemed to possess vast psychic abilities, such as interference, control, and reconnaissance. One could say it was akin to a Zerg version of a spirit inspirer.
Its abilities were special enough, and the means to control the rifts in alternate spaces, although not entirely due to it alone, were exceedingly useful skills for Su Han as long as there was a possibility to come in contact with them.
Besides, the gap in the physical form compared to the Titan Insect Beasts was not permanent. Su Han had every means to bridge it, simply by fusing with some large creatures similar to the Titan Insect Beasts, which would highly likely yield complementary benefits.
If worse came to worst, if the Insect Race descended again, catching a few more Titan Insect Beasts wasn't out of the question.
