@Gabriel does amazing work editing questions into shape - but I'm tired of approving his/her/its edits - is it possible for Someone to grant it/her/him the necessary rep so it's automatic??
Yes—after a fashion
In fact, each time you approve (or edit without rejecting) a suggested edit, you provide the editor with +2 reputation (up to 1000 total). So as you approve Gabriel's suggestions, you are slowly but surely pushing them closer to earning the ability to edit without needing review.
Obviously, that's not going to end the situation of you (and others) needing to approve edits any time soon. A quicker option, if you are willing to make the sacrifice, is to offer bounties on one of the questions they've answered. Ideally, pick a question that truly is interesting and where Gabriel's answer is worthy of a bounty.
But I'm afraid, there's no way to grant a proven editor the full edit privilege. It must be earned one way or another.
Unfortunately privileges on the SE network is coupled to reputation earned and not the amount of edits, flags or any type of "moderation" work you have done. This does make the SE system a bit of a bulky, crappy system for those who really are interested in helping with the moderation of a specific site/sites.
We who do participate in the moderation queues do get badges according to the amount of reviews we do, for instance, an amount of 1000 reviews in any review queue earns yourself a golden badge. But the fact of it, once you have reached your golden badge, there is nothing more keeping one in the review queue (Also one thing that does lead to users leaving review queues as there is nothing more for them to gain).
To come back to your point, it would be really nice to award privileges like editor in a specific field once someone has done a set amount of edits/reviews/etc. To be honest, I used to do quite a lot of edits before my 2K privilege, the same as @Gabriel, but @Gabriel I think has done twice as many as what I did. This is really by far the most I have ever seen, and I think half of my approved suggested edits is from his suggested edits.
I would not say I'm tired of approving his/her/its edits, but any user with so many approved suggested edits and with the almost perfect percentage of edits approved, it would really help if such user/s can get an edit privilege regardless of reputation earned, the privilege granted solely on the amount of edits done and suggested edits approved.
This is maybe something that the admins might look into in the future. This would most certainly help with site moderation on larger sites like stackoverflow