Not overkill, anything less than 4 camera POV’s is negligent if you have the money.
This is an excellent idea to maintain maximum image quality, and reduce recording malfunctions from multiple channels, and overheating.
You may want to consider going with the REAR cameras instead of IR INTERIOR cameras.
Why?
1.) The A229 Pro in 2-CH configuration with INTERIOR camera reduces the Front camera’s Bitrate from 60Mbps to 36Mbps.
2.) The A229 Pro in 2-CH configuration with REAR camera maintains the Front camera’s Bitrate of 60Mbps.
3.) The REAR cameras are 2K instead of 1080p, (and STARVIS 2 instead of STARVIS 1).
Of course they don’t have IR LED Emitters so you won’t see anything at night unless to turn on your dome light.
Also, you may want to consider mounting both “remote” cameras near the front A pillars looking diagonally to the rear.
It’s useful showing when you merge on the highway, or change lanes.
Or to record a traffic stop by law enforcement when they approach from either side.
Or you could mount the camera on the rear window to show the passenger compartment, and you will get an equal view out the rear windows.
Here is what the POV’s it will look like.
Here's what it looks like in motion;