Hi Peter, hi Ed,
Thanks Peter for anticipating this upcoming issue!
I think relying on a Java-based implementation of pack200 is a good idea.
Indeed, when pack200 is not shipped with the JRE by default, p2 wouldn't be able to use it anymore if there is no alternative. I think p2 has the necessary smartness (maybe some switches) to just ignore pack200 artifacts if we don't have a better solution by then.
In the meantime, I think the best strategy for p2 is just to wait until the removal of pack200 happens, and when it happens, switch to whichever best pack200 implementation (could be yours) or simply drop pack200 if it happens that the overall state of pack200 in the Java community reached a point where we can assume it's dead.
I do not have the feeling that p2 project and its contributors can be strong drivers about the future of pack200 here because everyone is busy with many things, and both p2 and the Eclipse world could survive very well without pack200 (updates would "just" be a bit slower). I guess pack200 is not critical enough to p2.
But that's an interesting topic to discuss with the community at large. I'll make it a topic for the Architecture Council to discuss. Maybe there will be more interest than I expect in actively keeping support of pack200.