Yes that's feasible. Years ago I used a home made PIC based devices to sit on a serial line between a piece of closed source software and a Sony tape deck. It captured and saved the serial data in both directions so I could later look at the data and use a PC to make it more human readable for debugging. From this a device was made to sit in the serial stream to correct problems the software had with some VT tapes with discontinuous timecode.
Using Arduino this would be easier to do now and if you know the command sequences being sent they could also be decoded on the Arduino.