Necroooooo'd
What bothers me about 8472 is how unsuited to their actual environment they seem. It's a giant blobby ocean of stuff, in which we don't see any planets or superstructures (but there could be).
This leads me to two possible conclusions:
1. There are larger organisms that 8472 evolved
inside, as parasites. These things may be so huge as to be continent-sized, and there may be living whale-planetoids deep inside fluidic space that are the heart of 8472's civilization. The bioships may have originated as the local equivalent of electric eels, and domesticated by 8472 as beasts of burden.
Episode ideas: The ships may have been 'uplifted' by 8472, and are now technically an enslaved species. A half-destroyed ship, now lacking crew, may reach out to another ship (the Crew's) and seek help. Of course, the ship may not understand that the Crew's ship is not sentient, or that it is
not enslaved by its crew.
2. The
entirety of fluidic space, from the dimensional framework, to the bioships, to 8472 itself, were created by
Arturis's people to overwhelm the Borg.
Episode ideas: Without Species 116's slipstream generators, the dimensional framework of fluidic space begins to falter, and 8472 has to relocate their civilisation to the Delta Quadrant. Having little regard for other species, they attempt to
convert large sections of the quadrant into Fluidic nebulae. Unfortunately, they'd destroy thousands of worlds in the process.