I am not sure externalizers would be a good solution. At least at some point I want to be able to do some operations on the grid without having OGM in my classpath necessarily. So if you use an externalizer, make sure your final format is OGM independent (for map/reduce etc). And in many ways, you can already do that in the InfinispanDialect by using a specific object rather than EntityKey as your raw key.
I am not sure externalizers would be a good solution. At least at some point I want to be able to do some operations on the grid without having OGM in my classpath necessarily. So if you use an externalizer, make sure your final format is OGM independent (for map/reduce etc). And in many ways, you can already do that in the InfinispanDialect by using a specific object rather than EntityKey as your raw key.