Roe females not being playable was simply because Galka were male only, and the original XIV races are based on XI's. Same reason why Miqote males weren't initially playable (Not sure for Highlander females though.)

Still think male Viera will be shown at the last fanfest, and the biggest reason they haven't been shown yet is because they (as well as the rest of female Viera's customization) isn't ready to be shown yet. Plus they can milk it to have people watch.show up at the next fanfest.

Easiest lore explanation is that just because most Viera, male or female, stay in their forest and follow tradition doesn't mean there won't be the odd one that goes against that. We've seen that already with Fran, nothing says that atleast one male Viera (IE the playable character) can't have also decided to go against the tradition of his kind.