Trustless distributed build would probably a long time in the future. From my understanding, Trustix is more about checking the build from independant builder. The problem is that being able to demonstrate that two builder are independant is hard, and you need to trust someone or something to demonstrate they are independant (but it would certainly still be less trust that trusting a single hydra provider).
However, safely distributing file distribution is totally possible with IPFS (or certainly others) (which mean Inter Planetary File System btw). Possibly including a signed “input → CA (and IPFS) hash” (with IPNS possibly being said signature). (but no one will probably have a latency more than a few seconds before a long time, althought this may help with load balancing and performance).
Also, the centralized architecture as used today probably doesn’t prevent using certains host under certains condition (if we ignore the fact that this might not even be a good idea to begin with due to fabrication cost, but I’m not knowledgeable with this). Internet is probably fast enought that transfering data to the other side of the world is totally possible and easily achievable. (even thought the builder still need to be trusted sadly).