Hi @ierturk ,
Thank you for using the community.
What you are trying to do is theoretically possible. Usually, for a task like this, you would also use the internal ISP of the Verdin iMX8M Plus for debayering and such.
Currently, there is a team of experts working closely with NXP to get this part of the chip up and running as soon as possible. Unfortunately, the progress of this is heavily reliant on the progress of NXP. As soon as they succeed it should be possible to at least connect two independent cameras.
For your case with 4 cameras, it might be worth to look at lattice for a CSI Bridge. Something like the one in the link below.
2 Input - 1 Output CSI Bridge
I hope this helped already. Please feel free to ask further questions.