Yes, I also find Jake to be a rather uninteresting character. He represents the possibility of a romance with vanilla sex.
On the other hand, Jake can play an interesting role in the story. Jake has desired this woman for years but has never had a chance. Only Kendra's intrigue opens a way for him to get closer to Anna.
He sees himself as the good guy in this evil scheme. Although he is involved in it, he believes himself to be something like a white knight for Anna—protecting her, if possible, from the worst consequences of the scheme.
But what happens to his ego when he finds out that Anna has already had sex with Marvin or with the other two guys from the office before Jake could make his move?
I don't know what MP is planning, but Jake's character is such that he could become Anna's worst nightmare. With his “male honor” wounded, he could really hurt and break Anna because she has romantic feelings for him.
Similarly, Kendra could then use him to hand David the evidence of Anna's infidelity, thus remaining completely in the background and hiding her involvement in the intrigue from David.
I also find it interesting whether Anna ever finds out about Jake's involvement in the intrigue.
Jake, as uninteresting as he is as a sex partner, can give the story a few nice and perverse twists.