I think you need to accept that in the cases of female single sex spaces, third spaces has been discussed for a long time.
And rejected.
Maybe even by your friends. Rejected because for some male people, it is not a safety issue, it is the women in those spaces being needed for whatever reason those male people demand. To validate is but one reason they demand access to the female single sex spaces.
Once women see this, then why should any woman support males accessing these spaces.
Just like the sports issue, what other male person who has 'worked so hard' to be who they are should be allowed access to female sports or single sex spaces. The logic fails every single time.
Sorry, no male has 'by no real fault of their own now might have something they care about denied to them'. Female spaces and sports were NEVER for them to access. Nor was any description of 'woman' theirs to take.
This might sound blunt and uncaring, however it is the raw and unvarnished truth.
Any male who has ever sought to access female spaces and sports on account of how they felt did so without once respecting the female half of the population. Whether they intended to or not, this was misogynistic of them.
If these males want to build their sports category to suit their needs, go for it. But instead, every one of those males who accessed female spaces and sports in this way needs to take responsibility that they chose to do so instead of finding a solution that worked.
Blame Stonewall. Blame allies. Blame women who told these males it was 'ok' when it never was. But a male who valued female people of all ages who did this need to take responsibility. Those people as a whole have not sought to find solutions - they were part of 'no debate' if they were there using the female spaces, words and sports.
I join you now in hoping that they can find solutions that work to fit their unique needs. But it is time to be honest about this.