Let's not. At least let's not if it comes out like it did in the previous BioWare games.
In ME2 at least there actually was at least one difference (in addition to the different romance options) if you played a femShep: during Garrus' recruitment mission you get treated to an absolutely playground level stripper joke by the merc recruiter despite the fact that femShep is armed to the teeth. Although the option to tell him to get lost is there... still, not a fan. The same in DA:O - after a character creation screen where you're told that men and women are generally speaking equal in Thedas and are found in most military organisations etc., you'll spend your first hours hearing how absolutely astounded everyone is that a Grey Warden can be / is a woman (not to mention the absolutely lovely gendered language which is the only stain in the perfection that is the Dwarf Commoner origin). I was not particularly impressed.
If there was some other way for the game to differ from a female / male perspective... then maybe, but honestly, I'm kinda drawing a blank on (cis) female-only / (cis) male-only experiences which could affect gameplay or story (assuming we're discounting pregnancy and childbirth and the like, and let's just... not. Sci-fi, fantasy and video games don't have a particularly good rap sheet when it comes to those subjects). I'd rather you be treated differently because of your morality alignment / reputation (along the lines of diplomatic / warmongering, trustworthy / untrustworthy, helpful / self-serving - but since the dual Paragon / Renegade morality system will probably come back, according to that then).
And when it comes to encouraging people to play different genders, I don't know if there's a lot you can do about that. Romance options is one way to encourage people to replay as a different gender (I rolled a male Inqy to romance Dorian, for example) but sometimes that's just not going to happen. I have about 7+ Hawkes, most of whom are guys, because I just prefer MHawke's voice actor over FemHawke's voice actor - and the opposite is true with Inquisition, where I am a dedicated disciple of the cult of Alix (because she's absolutely amazing IMO). In ME-trilogy, I have mostly femSheps in ME1 and ME2 because IMO Jennifer Hale was the better VA in those, but in ME3, I actually have about 50/50 femSheps and MSheps, because I think Mark Meer really stepped up his game for ME3 and I think there are scenes which he pulls of better than Hale. ...And the point of this rambling was that you probably won't be able to persuade players to change genders just by offering them an extra side of dialogue or an easier win-state for a side quest in a 40+ hour game if they have a specific reason for choosing their preferred gender to play as that the gender change doesn't directly or indirectly affect / account for.