Ok, I really like the idea of Lena becoming Seymour's sexy spy, seducing and then blackmailing business partners and sabotaging businesses to fail so he can buy them.
But, sorry there is always a but, it doesn't really make much sense. For the cafe to fail all Lena has to do is stop helping them. But either they are already failing because Lena didn't help them or Lena really cares about the van Dykes. This is not Star Wars where decent people become youngling murdering psychopaths in a blink of an eye. And to sabotage them she wouldn't have to do some sexy evil stuff, all she had to do is stop helping them. Which is not very exciting.
Spying on Emma would make sense in a way but there is no need for sexy stuff, all Lena would have to do is to pretend to be her friend. Again, not very interesting. Also I don't get the feeling Seymour is that concerned about Emma.
Seymour whoring out Lena to a business partner can easily happen but the problem with that is that you need new characters for that. So this would be more a one off thing, like with Ryan in GGGB.
I also don't get that Seymour is desperate to please Agnes, he seems quite eager himself. And the clause about him not being allowed to touch Lena except she asks for it, well, maybe he just wants to make her beg
So, while I think you are mostly right in that these things will happen, I don't expect it to be that hot and exciting. My theory for Seymour is that he is trying to break in Lena, to make her willingly accept to be his playting/whore/slave. Axel knows (and is likely helping) and that is why he was so calm to Lena after they posed together and why he isn't obsessed with Lena any more.
Talking about detective work, you have any idea when we will find out what is the whole ruckus about Stan?