I would work on flexion challenge exercises, not more flexion movements....but that's just me.
Side note:
The goal of the abdominals, glutes, lats ect. all of which is the "core" is to stop motion through the spine/pelvis and generate power through the shoulders and hips where the motion should take place.....punching, cutting/changing direction...all require a snap, a spring, a force generator like a whip.
Anyone who does hundreds of situps everyday is robbing their athletic capacity. You can equate the spine to a credit card or coat hanger. Eventually through repeated cycles of flexion/extension the spine will break (disc hernation).
Top MMA fighters who have reached their late 20's/mid 30's and choose to continue competing have stopped doing flexion/extension exercises because they have burned up their capacity to do so. Now, the smart ones atleast, save the flexion/extension for when it's really needed...in the ring. Just as soldiers should save their capacity for when it's needed, in the field, doing their job.
Hope this didn't come across as being a dick, I'm just pretty passionate about helping others avoid injuries, improve athletic performance smartly.