OK now--time for me to come back and argue my point back to you...
Starting with one thing I've tried to make clear in my points--we have never jumped through a subspace node and seen a Knossos for the first time on the far side of the jump. That being said, we have only traversed both directions after the discovery.
We always did it sort of like this (excuse the crappy diagram):
<<WHERE WE START>> ||knossos|| =================subspace================ ||exit|| <<WHERE WE FINISH>>
We discover a Knossos, jump though it from the Knossos side of the node, and jump out into space WITHOUT a Knossos. After the discovery, we can jump back from the side WITHOUT a Knossos to the side WITH a Knossos.
Next point... Knossos devices are ALL the same from the outside--it appears to me that they were mass-produced (there are 3+ Knossos devices, meaning that there are 12+ of each of the two unique parts). That being said, they would likely have to be ferried into position and calibrated to work as either stabilizer or destabilizer. If, in the condition, that they were stabilizers, how would the Ancients have known where to point the Knossos devices? Wouldn't they rather "practice" on a known node? If they can figure out how to calibrate the Knossos devices properly, there would no longer be anything stopping them from ever again expanding--they have the artificial means to leave galaxies.
Next point... either way the Knossos devices work, while "deactivated", the subspace node is undetectable. If everything in FS1, FS1:ST, and FS2 are correct, then a survey craft would jump though a new node and survey the stars, planets, moons, and all other physical features of a new system. At the same time or at a later time (I'm thinking at the same time), they would examine the subspace structure of a system and find other jump nodes. As the official node map states, Gamma Draconis was a dead and dead-end system--they found no subspace node and they didn't "catch" the Knossos device. When deactivated, it seems that the node ....
*NOTE* I lost my train of thought in 2 days. Anyways--I'm leaving on Sunday (last day around might be Saturday, though more likely today) for a 10-day event in Houston. Sorry I can't keep arguing my point--I'll try to get online for a few in Houston.