If all trunk-flexing exercises are out, I think you need to ask McGill what's left. I think he'll say stuff like TGUs, squats, deadlifts, and planks. I don't really think that McGill is correct in tossing all trunk-flexing exercises, and therefore I would ask whether you think weighted sit-ups, L-sits, and leg raises are verboten.

If all trunk-flexing exercises are out, I think you need to ask McGill what's left. He seems to recommend a modified lumbar-spine-neutral crunch called the "curl-up" alongside the bird-dog and side plank:

[McGill suggests] a core exercise program should emphasize all of the major muscles that girdle the spine, including but not concentrating on the abs. Side plank (lie on your side and raise your upper body) and the “bird dog” (in which, from all fours, you raise an alternate arm and leg) exercise the important muscles embedded along the back and sides of the core. As for the abdominals, no sit-ups, McGill said; they place devastating loads on the disks. An approved crunch begins with you lying down, one knee bent, and hands positioned beneath your lower back for support. “Do not hollow your stomach or press your back against the floor,” McGill says. Gently lift your head and shoulders, hold briefly and relax back down. These three exercises, done regularly, McGill said, can provide well-rounded, thorough core stability. And they avoid the pitfalls of the all-abs core routine. “I see too many people,” McGill told me with a sigh, “who have six-pack abs and a ruined back.”

McGill's recommendation isn't designed for your purposes of hypertrophy, but that seems to be because he intentionally disagrees with your goals.

In terms of programming these exercises, McGill's recommendations tend toward the extremely easy:

In general, we recommend that these isometric holds be held no longer than 7-8 seconds given recent evidence from near infrared spectroscopy indicating rapid loss of available oxygen in the torso muscles contracting at these levels--short relaxation of the muscle restores oxygen. The evidence supports building endurance with increased repetitions rather than holding time.

...

It appears low back exercises have the most beneficial effect when performed daily.

I don't see why a lack of oxygen is considered dangerous or unproductive. I also don't think you're going to see much hypertrophy from sub-10-second holds of these exercises. 

I don't really think that McGill is correct in tossing all trunk-flexing exercises, and therefore I would ask whether you think weighted sit-ups, L-sits, and leg raises are verboten. More intensive ab training (which includes McGill-forbidden lumbar flexion) seems fine to me if paired with intensive lumbar strengthening work like the always-beloved squats and deadlifts.