First, understand the Element3 bridle can be tuned for a more 'C'-like turn but de-power is progressively compromised as you move the towpoints outward. We have tuned it for quick turns and max de-power without pulleys.
Regarding your question, the E3 is sufficiently robust enough structure-wise to handle it and the # 1 bridle attachments are in a suitable location for a 5th (with an upper split) or to the center. My concern is the extent of de-power because the kite has a relatively low pitching moment (for drift stability) and the wingtip attachments are a bit aft which limits the AOA change. You could possibly get enough de-power with a loaded 5th but the extent of loading would effect the turning and likely destroy what you are trying to accomplish. An active 5th might do it but is a complex bar issue. The other option is short wingtip 'V' bridles with or without pulleys and a passive 5th.
To achieve it directly, I would build you a true 'C' with enough pitching moment to fully de-power. But, the Bar Pressure would be higher and you would have to limit the bar travel to prevent it from falling out of the sky.
Do you think if I set it up on five lines it would turn more like a Ckite. My idea is to have a hybrid kite that has depower but behaves as close to "real" Ckite as possible.