Wrting an Action to photomerge 2 images each of an entire folder

Photomerge is a Photoshop script that processes a number of image files.    Bridge menu Tools>Photoshop>Photomerge Invoke Photoshop passing Photomerge and Photonerge receives a file list to Process through BridgeTalk.

So you see it is possible for Bridge to Pass a List of File to Photomergs an have Photomerge bypass displaying its user dialog.  Therefore you may be able to batch stitch panorama using a script that repeatedly passes  Photomerge a file list to process. You would need to look at how Photomergs is scripted to see if a script can pass it a filelist to process. If it can be done you would need some logic you code to create the file list  for each panorama you want to stitch. Then pass  Photomerge  a list one at a time for the number of Programs you want created. The Script could also save and close each Panorama created as they are stitched. 

ACR Stitching is a different Process.  It may not be possible to automate ACR stitching Process.   ACR UI can be bypass to use existing ACR setting or default settings.  ACR stitching is not a setting so ACR UI most likely needs to be used. Raw file can be stitched via Photomerge for ACR would open the files into Photoshop as Photoshop documents. The Stitched Panotams will not bat an ACR generated DGN.

You can not accomplish task using Photoshop action, perhaps using script but I am not script guy.

For now let me provide you with info that photo merge can be done in Camer Raw. Select all images in Bridge then run ACR. In Adobe Camera Raw you can select two images then to run Photomerge > HDR or Panorama. I do not know for way to automate things inside ACR but at least you can speed up current workflow.

You can also use Lightroom which is part of CC and Photography plan. Again, I do not know way to automate task but at least it will speed up since it is using same engine as ACR.