Things are certainly becoming clearer. I am tempted to say at last
. And can I suggest you talk this through with a trusted friend or colleague before raising elsewhere, because if a MN audience that is inherently likely to be sympathetic to your cause got confused and abreacted due to misunderstandings, then you'll have to work all the harder on the messaging for the people you truly need to convince.
From my perspective, I think the nub of your discussions with colleagues to improve the process must revolve around the following: "There is nothing wrong with candidate A passing the bar because they got invited to 6 conferences last year. There is a massive problem with candidate B failing to pass the bar because (in spite of having the expected level of international reputation) they have been unable to attend conferences for whatever reason be it BF, illness or caring responsibilities."
In your shoes, I personally would be minded to solve the problem from a technical point of view by having the Dept set out some alternative methods by which a candidate who is unable to travel can nonetheless demonstrate their international reputation.
But that can only happen once the underlying issues have been addressed. These probably revolve around mindsets (e.g., "never mind the quality, feel the width"; or "we all know that the only thing that matters is hobnobbing with international colleagues, because that's what mattered when I was making my reputation" or possibly "look, if a woman can't sort herself out to get to an international conference, it's her own look out and I don't think she should be promoted" etc etc) or incentives ("I don't want to get stuck in this sodding promotions meeting with my 49 windy colleagues forever, so let's just use the number of conferences as a proxy, because it's much quicker" or "we can't afford to promote everyone even if we're supposed to, so we need some method of winnowing out the list, and this will do", etc etc). Somehow, these underlying issues need teasing out, and then people need to be persuaded to shift mindsets and behaviours, and then they themselves will look for the right solutions.
This is a non-legal approach but it is one I have seen work very effectively elsewhere in analogous situations. It is not easy, though.