Perhaps the answer is, rather than trying to 'adjust' or otherwise dilute the training standards for the existing SAS/SBS, you just create a new unit under the same SF umbrella for women.
That way, you avoid the problems of trying to make selection equal and in the longer term increase your numbers of SF operatives (you can then cherry-pick from the new unit when the Op requires it to work along 'regular' male SF).
It may, in time, lead to the full integration of females into current structure- for the truly exceptional ones - but in the meantime, give those ladies with all the requisite skills for SF (minus the crazy weight-carrying yomping) the chance to serve their country is specialised roles.
Someone did that already.
Meet the Hunter Troop: Norway's tough-as-nails female soldiers - BBC News