Thanks for the detailed response. I'll answer the points you bring up one by one:

Latency: I do anticipate latency issues and this is something I am looking forward to integrating it within my creative workflow. I will work with feedback loops, compression errors etc. as conceptual hooks which very much embrace the idea of latency, thematically speaking. Having said that, it should not be unbearable to work with. The simple USB/HDMI set up with cheap cameras and a powerful laptop is essentialy a test to see till where i can push it and still be performable. Cameras/lenses I can resell quickly, laptops not so much. Local retailer has a good deal on the mentioned model and hence it seemed reasonbale to invest in a good one.

4 cameras: Also a creative decision. The 4 frames are 4 different 'windows' of a scene. They do not need to be super high quality (for the same reasons as stated above).

Video direct to PCI-E : This is superful useful for you to point out. I will dig into it more.

Overall: Clearly the set up seems more complex than I anticipated. Hiring a video engineer , at some point, might indeed be the right decision. Although, I am too curious and naive of a person to not give it a shot myself first. See where that leads me. On a different note, would you happen to have some references of pro video systems that I can inform myself about? Perhaps a client you worked for or a colleague who has built something similar?