OP I appreciate your constructive approach but I think Stonewall genuinely DGAF for women or for LESBIANS.
Which is pretty fucking horrifying when you think who helped to build Stonewall into the household-name supercharity that it is now. Not to mention Stonewall sticking to Stonewall’s legal charitable objectives.
I think there is nothing to lose by calling Stonewall’s bluff- women do want debate about their concerns, though Ruth Hunt’s response seems to be #nodebate.
So you would be positively pointing to the open door to dialogue. But I’d agree with the PP who have zero hope for any meaningful engagement from Stonewall.
Stonewall know very well already what gender critical women think because they are active on social media, they know full well what women are saying about their concerns- but Stonewall DGAF.
Stonewall condemned the lesbians protesting AT PRIDE about the erasure of lesbians by the TRA agenda. Stonewall said Get the L Out shouldn’t have been allowed to ask the questions they asked because saying those things made trans people feel ‘unsafe’ 
Totally ignoring and denying and turning the tables on the concerns of the lesbians who feel so undermined in THEIR community that they bravely stepped up and protested at the PRIDE parade. DARVO.
www.pinknews.co.uk/2018/07/09/stonewall-slams-pride-in-london-saying-organisers-had-a-duty-to-act-and-protect-trans-people/
Stonewall’s intolerance and hostility to these women’s concerns was reflected by other organisations like London Pride who were rounded on by Stonewall and others for letting the women protest, then issued a very aggressively-worded statement condemning the ‘vile’ protest and saying this kind of speaking out should be ‘stamped out’ 
To me this kind of inflammatory language gets close to inciting violence.
www.pinknews.co.uk/2018/07/08/pride-in-london-condemns-anti-trans-protest-as-vile-says-we-are-sorry/
Basically those reactions are confirming everything that Get the L out are warning against.
Stonewall are utterly complicit in that.
So I think yes if you want to offer a dialogue the absolutely do so, but it would be important for the record (and for anyone not familiar with these issues) that any open letter emphasises that women have always been open to talking about their concerns, but are being shut down and condemned when they do try to air them. The door has always been open. These are not two, equally pig headed, equally not listening sides. No gender critical woman has EVER sought to silence or threaten, doxx or get anyone sacked for asking questions nor has ever called for #nodebate.