I tried this once, note the key word "once".
Photomerge smudges pixels around during the process and never the same way twice which makes the layered HDR conversion process virtually impossible...they won't match up.
So ya say okay, let"s do the HDR part first...how do ya make sure every group was processed exactly the same way...create an action of course. Can ya do that?
In my case, using CS4 at the time, photoshop wasn't able to balance the colors during the photomerge process to my satisfaction...they didn't match up.
Lastly, can your computer handle the processing power necessary to preform these labor intensive tasks? My old 4 GB RAM machine wasn't close to have sufficient power, kept getting "out of memory" messages.
Ya might want to reevaluate your desires or...give it a try and let us know how it turns out. 
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