Couldn't you handle the Spine and Spriter animations the same way once they are imported?
Or is there a licence problem with the way of the Spine implementation?
Spine animations are played back using the Spine Runtimes, and to legally use these runtimes in your games you need to own a Spine licence.
So even if the Spriter animations could be made to work with the Spine Runtimes you would still need to own a Spine licence, at which point you may as well use Spine.
Spriter would need to be implemented separately using its own Runtimes under the terms of that licence, or written from the ground up, so an extension as posted above is probably your best bet.
There are threads on this subject already, as well as DragonBones - do a forum search.