I don't believe the problem is 'reviewing' changes, not in the technical sense. I think the problem is owning the changes once they are released. If I release a patch in p2 that makes its way to Tycho, that produces an incorrect repo, which causes the release train to grind to a halt -- I'm responsible for that. Of course the author of the patch was happy to take credit for the great work, but when push comes to shove in the middle of February and Luna M5a is broken -- I need to fix it. And I either need to explain to my boss that this should be done on company time, or I need to explain to my 6 year old that I can't take her to soccer.
If the original patch was provided by a competing company to better enable their product, it won't be easy to convince my boss that this is a good use of my time. The best code review system in the world (read: Gerrit) won't help here.
A reviewer must not only review the change, but also take responsibility for the code once it's released.
Finally, one of Linus' strengths is his ability to say "NO", this idea is crap and it's not going in the Kernel. WONTFIX isn't something we do well at Eclipse.