There is a significant risk that closing the age gap could exacerbate the problem rather than alleviate it by narrowing the window of opportunity for the girls. Since most boys will not consider a girl older then themselves, a girl would find herself ruled out by the majority of the boys on the market after just 1.5 years in shidduchim under your proposal, instead of the current 4 years. Of course you can try to change the boy’s mindset, but this will take time and is not guaranteed.
This is another example of why the problem and its potential solutions need to be more carefully thought out before radical reforms are implemented.