Personally, I would be very happy for the Promise to be reworded to match the Canadian Guides version. Maybe that's because I'm a Brownie leader, where we promise to love our God, so are already a bit closer to the Canadian Promise than the Scouts who (a bit of Googling shows me) promise to do their duty to God.
As for the 2 questions:
As I said, I would be happy to amend the Promise (and have amended it for girls who did not want to say it in its original form) and I don't want to exclude any girl who would enjoy and benefit from being a Brownie. Guiding has changed a lot since I was a Brownie and Guide and it seems that the wording of the Promise is under review.
Even so, I don't think bandying the word inclusive gets us anywhere. Like most voluntary groups, including WF, Scouting and Guiding are inclusive of anyone who supports their general aims. Certainly, I think there's a debate to be had about how far the general aims of Guiding are faith-based and how much the organisation would change if the references to God were removed from the Promise. But, it seems to me, complaining that Scouts and Guides aren't completely secular is a bit like complaining that your child's violin teacher hasn't taught them to play the tuba - that's not (as things are currently set up) what they're there for.
I take the point completely that atheists may feel uncomfortable with the Promise, but in a way that isn't the central problem. Our pack meets rent-free in a church hall. We are therefore literally indebted to the church. Anyone who wants a completely secular experience is going to have to find some accommodation with that, too.
Out of interest, how does WF accommodate people who are out of sympathy with some parts of its general aims? I doubt that anyone would simultaneously want to be a member of WF and (say) Army cadets, but what would happen if they did?