[quote=ChibiYuki]
Considering the knowledge we have about Mod-Souls, much is unknown about that and it is plausible, but then there is the possibility of having them adapt considering they are artificial life, they in sense have to adapt. And those Modified-Souls who don't simply die or last until they are overwhelmed after what their pre-set abilities can do.
[/quote]

They were never designed for growth, they were designed to make humans less worthless and usable for military purposes, not to create artificial shinigami.

They are, in essence, not so much artificial life as they are a artificial intelligence that can be injected into bodies to improve their capabilities.