To my knowledge bio-modification is a batch of teeny tiny nano machines that break down and rebuild your body during the process in a controlled fashion at the genetic level. A complete do over essentially of every single part of your body. Obviously there is hand waving all over the place. But the central grasp is break down and rebuild.
So, with that in mind, you could pull from genetic diseases that break down the body. Not wishing to touch on things that are sensitive or triggering, but cancers, radiation, degenerative diseases, necrosis in the deconstruction.
Then on the reconstruction, granulation tissue, fatigue, hunger, thirst, starvation and dehydration even as your body works over time with those nanos to build new cells and so on.
If I have not grasped bio-mods after doing what I have done in game for as long as I have.. I have zero idea what they are at this point.
IF we are looking at specific scripts and strings of descriptions I can work on something, if the above is fitting.