I've found two Chimeric Biomasses in the first three planets I colonized - the first being my Homeworld.
I wouldn't look that gifthorse in it's mouth and use those 6 Archives. To The Max. Research all Precursor knowledge - Centers, etc - to make the best of them.
It sounds like the RNG just went and rolled your way big time.
As to whether the AI knows what to do if it finds itself in the same situation, I don't know. You'd hope it does to make the game as easy for it as it would for you...