Agnes is a woman. When I suggested that Seymour doesn't like sharing his toys, I was of course referring to other men. Obviously at the moment, Seymour is not actually Lena's lover, and he's still trying to manoever himself into that position. So in the meantime, she's going to be having sex with other people, and Seymour can't affect that. But when he does get into that position, I think we'll see a completely different reaction from him.
Axel being in that shoot, was not originally Seymour's intention. He allowed himself to be persuaded, because he wanted to please Agnes, who will be a useful ally to have, especially if he wants to promote Lena's career as a model. She obviously has a sexual attraction to Axel, and she just wanted to see him naked, and Lena's involvement in that scene was academic from her point of view. Your insinuation that Seymour allowing Axel in that photoshoot, is evidence of his willingness to allow other men, including Ian, to get involved in sex games with Lena, is simply not bourne out. Axel was in that photoshoot purely to satisfy Agnes, and had absolutely nothing to do with what Seymour hoped to achieve with her.
It's interesting that you mention Nietzsche, because until the last update, it wasn't possible for Lena to select him as her favourite philosopher, or choose to be 'the child', because of a bug. When you do, it's noticeable that Seymour is taken aback temporarily, because Lena gets the better of him, and he can't come out with his spiel about him being the child/master as effectively, which is him saying he's superior to most people, and by implication Lena. He quickly recovers though, and gives her an evil look, and says her being much smarter than the average person, will just make everything more interesting. It's like he's saying, it will just make his conquest of her, all the sweeter.
But I wonder, if there will be a pathway, where she will ultimately turn the tables on him? Because he's not quite as smart as he thinks he is? So Lena choosing 'the child', may be part of a later option, where this might happen? If she's on the cuck route, Lena becomes increasingly dominant, to the point she laments that Mike isn't as obedient as Ian is. If he were, she could make him end his relationship with his girlfriend. So I'm wondering how far this is going to extend? Will there be a possibility for her to become dominant eventually, and this is the beginning? And ultimately, even Seymour and Axel will be made to bend to her will? In the scene with Axel, doesn't Seymour suggest even Apollo can't resist the allure of glamour, and must bend to it's will?
I also play her as submissive, and until I saw what was behind 'the child' choice, I assumed that Lena could only take a submissive role with Seymour. But now it occurs to me, why shouldn't she end up in a dominant position. Eva does tend to have a lot of different pathways in her games, so there is really no reason why we shouldn't end up with a dominant Lena? That choice reveals a slight chink in his armour, and perhaps underneath his seemingly supreme confidence, there is an element of insecurity, that he just hides very well.
Nietzsche described three stages of development, by which a person can achieve freedom. And everybody starts off as the Camel. You don't just automatically become the Lion or the Child, as Seymour insinuates. For Seymour to be the Child, he would have had to be a Camel himself initially. But Seymour believes that he's always been set apart from normal mortals, so naturally he's always been the Child. But that's a misinterpretation of what Nietzsche was trying to say. Which is probably why he equates the Child with being the Master. The Child is the master of his or her own destiny, but that doesn't literally make him a Master. As Seymour obviously believes. That's how the Nazi's twisted Nietzche's philosophy, to fit there own perverted agenda. And Seymour is effectively doing the same, to justify his own questionable actions. I think he also believes ( in his arrogance) he can reach the fourth stage ( the Overman), which Nietzsche suggests is unlikely ever to be achieved, but which the Child constantly strives for.
My guess is, that Seymour ultimately hopes to make Lena into a 'Master' as well, so she'll become a worthy companion for him, and ultimately someone worthy to inherit his fortune and continue his efforts to control Baluart.