I like the idea, particularly the bit you said about Kain’s original capture weakening him as well, but no data to support or discount this hypothesis can be found in the film.
The scene where the operative was giving an exposition and it showed Kain’s capture, whether he lost energy or not is debatable I admit. However the scene did show Kain taking damage, at least that’s what I think from the amount of screaming of he was doing. Damage from massive Juraian energy focused on him would have taken a lot out of him and would take time for him to recover.
Also if Kain’s prison was made of combination of Jurai and GP tech, then his cell might have been lined with Jurai energy, like padding for insane patients. His energy would have been kept at bay while he was in his cell by the Juraian power if that was the case.
Lastly I would like to correct myself when I said “space time prison” in my previous post, I mean to say subspace network.
