I'm not sure the "James Bond" thing was meant so much for a battle form as what Lasciel would have augmented him into the rest of the time, in social situations and such.
In terms of combat, presumably she would have been trying to build on what he already is, instead of turn a caster into a primarily physical fighter. So count on supercharging his spells with Hellfire, and otherwise mostly focusing on improving his survivability. It's not a form, but she probably could have taught him to improve the defensive enchantments on his clothes to something commensurate with Eb's, that gives a sort of force field even over what's not covered. Likely augmenting that with the same protective smoke around him that she was doing with Hannah.
I doubt Harry and Lasciel as a pair would have gone heavy on the shapeshifting - maybe toughened skin around the vitals and arms for fighting anything with claws, and some extra muscle in a pinch. But I'd guess down that path Harry probably still would have preferred in the longer term to do extreme exercise and use the Fallen to accelerate recovery between sessions - basically what he's doing with the Winter Knight path, only primarily for fight-preparedness instead of as strategy to keep the mantle tired.
It would have been an interesting arc, if the story had gone that way, between Lasciel teaching him enough advanced magic and going along with supporting workouts that the decision to pick up the coin seems rewarded, but vastly preferring improvements like the smoke and shapeshifting that push him deeper into dependency. Vs Harry knowing that's her game, and being way more interested in learning new spells that he can then use on his own, and putting on his own muscle even if she's helping.
