Hornbeam are great for bonsai. E looks like a good point for a cut, maybe after doing a layer up just a bit higher on the trunk, just under the G branch.
The problem is taper. You can have movement in the trunk and no taper, but if you have no movement, and no taper, well, then you need flowers!
One interesting consideration is the root system. See the Strong A & G branches that point in the same direction? Now look down at the roots and it appears that the root system is largely one-sided. Usually there is symmetry between the root system and the canopy, so the imbalance in the vigor of the branches suggests there may be a defect in the balance of the roots.
It might be best to get down into the soil before you decide which branch and therefore "front" to use in your tree. Otherwise you might be looking at a ground layer to restore the root system. This isn't a bad idea, by the way, but you should know what you're getting into if you choose the wrong "front"
Regards,
Matt