Oh well. Boa's devil fruit is basically pretty hax already. It should be the Petrify no Mi rather with the love stuff as a bonus, since she is able to turn the areas the touches/kicks into stone, totally unrelated to the target having fallen in love or showing signs of affection towards her. Of course, one could argue that even in a battle scenario her opponents may still have perverted thoughts in mind which in turn enables Hancock to make them crumble, but that is still a big question mark.
What remains is a power able to take out masses of fodder in an instant and to effectively damage every opponent easily no matter if they have armor or not. Momonga widthstood her powers, which greatly affected him as well and redered him useless if you remember, only by deliberately hurting himself. Every male character except psychopaths like Doflamingo and entirely naive guys like Luffy (although I think Luffy is the only one in the whole One Piece universe who reacts this way) will be affected by Boa's powers no matter if he wants or not. And if the choice is between losing focus on battling her on one hand and hurting oneself on the other I would say she is a pretty powerful beast.
In addition, her haki has been portrayed as more like an aura which the Admirals also showed during the Marineford Arc. It is still unclear to me if Oda did that deliberately or if he just decided that he needs to portrait haki as black coating now to make things more obvious. The fact remains that Boa Hancock has proven to possess the necessary tools to deal with Logia users, Pacifistas, Vice Admirals and masses of fodder without even breaking a sweat. Therefore it is only natural to assume that given the necessary motivation, she would definitely be able to hold her ground against an Admiral. To which extent the Admirals will be affected by the love-focused side of her devil fruit I can only speculate about, yet the fact remains that she has powerful haki, incredible physical prowess and petrifying abilities that will help her even more against Logia users who underestimate her.
The only uncertain thing about her abilities is the question about her CoO abilities and her speed. Given the fact that Akainu and Fujitora seem to be fighting like bulldozers the only known Marine ranking higher than Vice Admiral who could prove to be a problem for her would be Kizaru, who I don't expect to take the fight serious enough but whatever.
Many of my points are of course based on extrapolation of known facts. In my opinion Boa could as well be one of the four Yonkous replacing Big Mom, although I can only really make that assumption after seing Big Mom in action and what actually defines her as Emperor.
Edited by Qbix, 01 January 2015 - 08:08 PM.