Good mention on the etak thing. Etak as huge box that does it all is unlikely. It could have been as simple as modifying the communications array to emit quantum pulses. Quite literally it probably was like that, etak itself is probably just information on how to create quantum pulses with known communications technology and software. Etak is better referred to as a method for creating quantum pulses. After that a laboratory for etak onboard still makes sense too (that's the top secret location where they study and work on etak to perfect, and possibly could have also been the room from where bosch sent messages to the shivans (only bosches immediate subbordinates knew anything if little knowledge about etak, after etak laboratory is usually referred to as being off limits with only bosch having and a couple of other people having admittance to it's information, so a restricted area on ship used to type up messages for the shivans is like a no brainer, after that the rest of the iceni crew can't decipher the quantum pulses coming from it's own ship (only bosches immediate subordinates had knowledge of etak)). Keep in mind the rephaim was able to send transmissions to gtva vessels, which suggests that etak worked through the iceni's existing communications array to send transmissions to shivan vessels, and even suggests that etak was not as crude as sending quantum pulses over dead space, but rather using a standard transmission, just making sure that shivans hear quantum pulses coming out of the transmission when they receive it on their end.
The way etak is described by freespace isn't really good. The iceni itself sending out quantum pulses into dead space sounds extremely crude. I mean it's proven that shivans can send gtva ships transmissions, that means ships can send shivan vessels transmissions too. It's just that the shivans possibly don't understand the words coming out of your mouth, as much as we don't understand quantum pulses. You don't have to send quantum pulses over space itself, you just need to send a standard transmission to a shivan vessel, and make sure that what they hear coming out of the message is quantum pulses. Judging by a species that lives in a vacuum they don't hear sound, they probably don't have ears, also why speaking in quantum pulses is necessary when in space for the shivans. So capturing a shivan communications array was probably vital for etak. Humans have some type of a transceiver with a speaker and a microphone (at it's most basic thinking) so you can receive messages hear them, and talk back. So what the hell is the shivans version of a boombox speaker to them? Let alone how a shivan computer interprets data transmissions and quantum pulse transmissions. In order for etak to work, is understanding of how shivans receive quantum pulses on the other end of a message being sent to their ship is like a no brainer for necessity, so that means scientists at gti were studying a shivan communications array.
In essence, etak is probably software which is an in the works english to shivan translation matrix, and then the other half of etak (if not the whole) is sending the correct kind of transmission that a shivan will "hear" coming loud and clear from the inship quantum pulse speaker (of course a shivan speaker probably doesn't output sound, but rather only quantum pulses).
Shivans can receive transmissions from gtva ships and send them back, it's whether or not you're sending a standard transmission that comes out as quantum pulses on the other end that matters.
Keep in mind quantum pulses are to shivans as sound waves are to humans (shivans live in space with no atmosphere, that means no sound, don't try to think that shivans have ears that recieve sound waves, or else they'd most likely decipher english during the great war, and have just plain old blown up the iceni even when the iceni is talking to them..shivans do find communication interesting i just doubt they can interpret sound as language as we do since they live in a vacuum), like i said, scientists probably had in no doubt to study a shivan communications array and computer systems.