The main core problem is not truly known. The observation is - the retention of women is low. We have tried various methods of general retention. More classes. More basics classes - now we are specifically reaching out to women.
As with many dojo, and life in general, there are always a few men who disrespect women. Unfortunately, their actions can be the final push on their way out.
The intention here is not to male bash, or get into a gender discrimination debate. The intention on this forum is to gather useful tips that will help us start a short term women's aikido class
I know you don't think my suggestion works and is the way to attract women, but women just aren't attract to an pure Aikido class. Since you tried various things to attack women and they don't seem to work, it was for me, useful to understand what women want is that tightly toned large muscles groups, and low body fat. What they don't want is feeling vulnerable.
See Muay Tai, Tae Bo, kick boxing gives the average women a feeling of empowerment. Aikido gives that power to women when she is the Shi, but then takes that away when a women is the Uke. They get that feeling of vulnerability when being the Uke. Women don't like feeling vulnerable. They don't seek out things that will empower them and the things that will make them feel vulnerable, moreover when feeling vulnerable. They also don't like hiting the ground and having their face where peoples feet have been.
My tip is, that you have to change Aikido for women to attract women to Aikido in the numbers you are looking for. I understand why you don't want to change Aikido in this way, but it might be the only way to get the results you are looking for.