This is a good topic, IMHO.
Personally, I believe that Mab considers the marriage very important. It's a contract, it's high magic and it will be very public -- all of which Mab, Harry and Molly talk about or think at various points during the final chapter of Battleground.
It will bind the White Court -- through Lara -- to Winter. It will give Harry protection from, and separate him further from the White Council. Mab can hardly be unaware of the fact that Harry's connection to both Winter and the White Court was the pretext for expelling him.
Molly is not a suitable candidate for the Queen of Winter. She will be one day. But right now, the man she loves, her parents, her brothers and sisters and their children are all alive. In a hundred years when the people she knew as a mortal are all gone, she will be more prepared to have mastered her emotions and act as the ruthless calculating machine that is needed to protect reality from the Outsiders.
The Winter Lady isn't a crazed ball of hormones, unsatisfied lust and megalomania without a reason. If the Winter Lady is an apprenticeship for the Winter Queen the Mantle of the Lady is testing her in the most brutal way possible to control herself and act rationally.
Now Lara, at this instant in time, is actually a much better candidate than Molly for Winter Queen. While she also has some passions, she's had centuries to train her self control and to engage in the ruthless machinations of the White Court. She's also shown her rational side by making good use of mortal "ferromancy," and hirelings. This is in marked contrast to many immortals, who disdain mortals and see them as cattle. Lara is different -- more like Odin and Mab -- as Lara sees humans as resources to be developed and carefully exploited in a sustainable way. It is a very short step from this to protecting them, we take care of resources that we own but "ruin the commons."
Interestingly, I wonder whether Harry and Lara might be able to "know each other" in a biblical manner, as man and succubus. Possibility A -- the Winter Knight, like the adolescent big foot, is simply too large of an energy source to actually be consumed by Lara's hunger. She could draw on Winter, but Winter is simply too big to eat. Also, Harry notes that extreme exercise helps him keep Winter at bay. This reminds me of Justine, who's emotional state was settled by Thomas' attention. Possibility B -- Winter can quiet the Hunger. Recall Auntie Lea putting Susan's hunger to sleep. True, it knocked out Susan, but the Red Court's vampirism is MUCH more profound than the White Court's. I suspect that the original White Court vampire was a pre-White Council wizard who studied the Red Court and tried to over come their weaknesses. Essentially, he cut a deal or performed a ritual to try and achieve immortality.
In either event, this could be a win-win for both of them. Lara gets fed without killing mortals; Harry gets Winter put in check, plus sex-vampire nookie. As I said, win-win.
A final thought. It is interesting to me that the White Court "oath" is shared with the Outsiders. "Empty Night" is used by both groups. Surely, this is not a coincidence. Is this a relic of Lord Wraith's dabbling beyond the Outer Gates? or is it something more fundamental. McCoy has shared that something is behind Harry's phrase of "Stars and Stones," and it's likely that "Hell's Bells" has some significance to the plot as well.
