In the world of Industrial Automation the RS232/485 port is still very common for programming older and small scale PLC’s (Program Logic Controllers). Some of these systems are over 20 years old and are based on these older communication standards.
Most programmers for PLC’s typically have a older laptop or desktop that is running Win 7 so that they ack address these older systems. From experience the USB to 232/485 dongles do not tend to work with WIN10 and specific external interfaces that convert E-Net to RS232 cost over $1000.
Looking at the modules, RS232 won’t physically fit. I think the external port will also have stronger grip than the module itself and will be USB under the hood anyway.
You’ll be happier with a $60-80 standalone USB device with properly WHQL signed drivers.
It should be possible to do a RS232 that bumps out from the form factor of the card (like we are planning to do for Ethernet). As @RandomInsano notes, that would still be USB to RS232 under the hood, using something like an FTDI bridge.
I would like to add my two cents that, to me, de-dongle-ing is one of the benefits to the expansion cards concept. I use RS232 and Ethernet on the regular for my job, and I appreciate my work laptop laptop with the ports built in, having to manage a bunch of dongles along with my interface cables is a bit of extra hassle I would like to avoid.
I’ve had good success with FTDI branded USB adapters in the past, I think putting one in an expansion card would work nicely.
It would have to have the screw mount removed or be a modified RS232 with no screw mounts to fit length-wise in the card. So it would functionally work for quick-connect (Like VGA Ports on Laptops) but would not be good if you would need it to stay in your laptop constantly @Dillon_W.
Here is the thread for a RS-232 converter with a rj-45 port, it is for interfacing with routers but can be remade for DB-9/RS-232 and serial interface. Still under testing.