On the topic of gender-preferences. It seems the core of the request would be: "A choice of gender-toon". This would be a good request in itself. Unfortunately (as stated before), it conflicts with the story-driven elements of the game.
Now, onto personal preference. I for one like it that the expansion features a character from the original game. Add to that the fact that I have no qualm playing a game with a female toon, I support the devs current decision in this.
As to why people have trouble playing games that features a woman, I don't think we'd get definitive answers on this. I know my better half likes games a lot better when she can play a female, since it's easier to associate with the toon (She did like Duke Nukem, by the way). In that regard, I cannot but respect the same point of view for males that dislike playing female toons, even if I don't share their sentiment.
However, I do feel the argument that the main player base is male, is not as true as many males would like to believe - at least, not for games in this genre. Kings Bounty, The Legend has much that appeals to (the many) female gamers I know. Two exambles would be that it's graphically pleasant, and that it has a very good story in which the options that are offered to the player support kindness as much as 'gruesome slaughter'. Games where it's mainly numbercrunching, killcounting or grinding are often considered to be more 'to the male's liking' and less so for females. Games that are aesthetically pleasing and hold a good story, have a large female playerbase.
So my guess would be that for many of the males that are 'lost' due to their hesitance to play a game featuring a girl, there will be women picking up the game instead. (For instance, the wives of the men that stopped playing
Summarizing my point: The game features a story-driven experience that in my opinion more than compensates for the lack of toon-customisation. I'm quite glad the devs can make the decision to cut their losses in a certain segment of the male playerbase, so that they may offer us a sequal with the same (or even better) quality: a strong story. I cannot think of a male toon that could be substituted for Amelia and not make the story awkwared (if not at points downright emergingbreaking).