Inflatable superheroines scenario

There was a topic about this stuff, but it was mainly concentrated on whom to inflate, not the story.

So, hope you don't mind if I start a new one :P For I have an idea in my todo list, which is not thought-through/detailed enough to start writing.

Here it is:

 Well, there are two villains. One woman who wants to be huge and powerful, but currently is just a pathetic mortal (Giganta maybe?)
Another bad guy - a warlock who uses her to pursue power and world domination. He prepares a rite, that can transform a woman into walking inflatable doll, with her power proportional to the size (bigger = stronger). She also will be bullet proof. Her only vulnerable point is her inflation valve. 
 He politely omitted the fact, that transformed woman becomes subdued by the man who recites the spell. So she'll be all powerful slave, like a genie. Besides that, she's in fact a sex-doll so she also wants to pleasure her master sexually. Warlock is looking forward for this as well, yet business is first. Pleasures may wait till after world is at his knees.

 On the good side there are military, police (useless obviously), Wonder Woman and a good guy (just a high school boy probably).
 Wonder Woman quickly finds she can't deal with the inflated giantess, but she's able to find the scroll of the rite. She needs someone to read it and make her match for the giantess. Of course, she doesn't know about side effects as well.
A boy who happens to be around, helps her by reading the spell, while she stays in the pentagram. She transforms and finds that she wants this guy badly and obeys his every word. But he orders her to go fight the bad guys first. She inflates and heads to the heat of battle. (I think she can inflate herself if given such an order, just inhale, no gas tanks contain that much air. Yet on the other hand, inflating her via hose, through valve would be sexy).

 Epic wrestle between two giantess follows. They can't damage each other. To defeat bad Giganta boy has to crawl onto her back, find the valve and pull the inflation plug. This is the race against villain, who is crawling to the plug of the Wonder woman in the very same time.
 They both deflate simultaneously and villain gets arrested. As to the WW and the good guy, they'll enjoy some leisure once he reinflates her.