Want to preserve shared photostream for subscribers but erase everything on my device
Do not worry about wiping your device to sell it. Shared Photostream is entirely in iCloud and tied to your Apple ID. Wiping your device does not change the status of anything in the cloud. I have wiped devices at various times and signed into various devices - always to have the correct Shared Photostreams appear - ones that others have shared with me and ones I have created myself. 

Aside from that, your question is complicated. I am sure that there is no way to transfer ownership of the iCloud Photostream. Your subscribers will have to either save all the pictures to their devices or one could select all of them and create a new Shared Photostream. However, all of your comments and likes will be lost during that transition. 

Regarding your Apple ID, I certainly recommend you do not change Apple ID. However, if you do not have any iTunes, App Store, or iBook Store, and don't mind changing it, I suppose it would be an option. However, I believe there are better ways. I have observed others dealing with multiple Apple IDs and it can be a terrible frustration. 

So again, wiping your device is certainly not a big deal, and don't change Apple IDs. Sign back in with your same Apple ID on your new iOS device (if iCloud backup was on) and all your pictures, settings, apps, and documents should automatically come back.