For better or for worse, with the new Astra Militarum codex under our belts, we have an answer on the current rules for Chimera's being updated for other armies with access to them. The answer for the moment, is not yet, and nothing is in the works. And here I was thinking we might see an faq answer, or something easy.
Please remember that even though was a response from the Black Library, something could be in the works.
via a reader on Faeit 212
I received today the answer from BL regarding the Chimera's rules on other armies:
Thank you for your email, my apologies for the delay in my reply. We do not have any current plans to update the rules for other armies that can take chimeras, but this may be something we look into in the future.