IS it too early to let John Adams take a senate seat after his Presidency, die early, and have Abigail appointed to succeed him? From what I remember of her, she was a proto-feminist and would have been a well-spoken person who might have convinced enough people that women could understand the issues of the day that she could perhaps get them to start educating girls earlier, etc..
So...
Washington chooses to only serve one term, as Adams convinces him that he may quit otherwise, because "I am nothing int hsi job, and you, Sir, are healthy and hearty." An aide tells him, "Why, this job has drained more of your health than anything else could. If you reture you may have 20 more years."
John Adams becomes the 2nd president in 1792, and appoints his son to some minor post, hoping it will help Charles' alcoholism. He, in turn, doesn't die from alcoholism, but in the early 1790s, "finds religion," as some call it then, and survives. While he isn't a major political figure, this prevents Adams' depression afterward.
With Washington's advice Adams is able to steer clear of trouble amidst the wars of Europe. John Adams chooses to serve two terms, with john Jay as his V.P. each time; he is not "breaking tradition" because, in most peoples' minds, Washington hadn't wished to be there, anyway, so his was not strictly a "one-term tradition." rather, it is Adams who develops the two-term one.
However, Washington's help on a few key issues during Adams' term does breed a sense of former presidents being used to help advise and consent to things. It is therefore easy for John Adams to accept a Senate seat in 1803, wherein he faithfully serves for ten years. Washington's help from afar, meanwhile, butterflies away his sickness and death.
Washington's influence helps Virginia to adopt a policy of gradual emancipation. Adams' constant fight - which may have caused his health to deteroriate - to avoid slavery in the new Louisiana Territory also has some effect on it.
John Adams contracts an illness during a visit to the South - he has been an opponent of slavery for eleven years in the Senate. he dies on July 4, 1814, the same day as Washington. His final words are, "George Washington still survives, independence forever," not knowing Washington had died the same day.
Months of confusion persist, during which Congress refused to seat one potential Senator for being part of the Hartford Convention which favored secession during the War of 1812. Finally, the Massachusetts legislature, fed up with Congressional stalling but also wishing to honor the late John Adams for a little while, appoints Abigail Adams to fill her husband's seat.
Abigail surprises many with her steaking ability, and eventually it is decided that she will serve out her husband's term, till 1817. The appointment - which some say was downright satirical - shows that she has many of her husband's ideas, but she is also more liberal in others. She continues John's attacks on slavery, and shows how women everywhere can be leaders - or, at the least, allowed to vote for leaders.
By now, Virginia doesn't allow new slaves to enter, and will totally outlaw slavery by January 1, 1830. Much of this is compensated, but it means there is no slave-free balance. As other states see how effective this is, Delaware takes the bold step of following Virginia - they and Maryland are surrounded by free states, anyway.
The Adams' work emboldens others, and while the 3rd straight Virginian is elected President in 1816, this is actually good in that is keeps Southerners from thinking that the Northern abolitionists will rule everything.
When 1820 came along, thigns are more favorable to free states, as Missouri is admitted as one, somethintg most peple had expected would happen, so there wasn't a huge slave population. Though Abigail was dead by this time, her efforts had left a lasting impression; schools were built to educate girls as well as boys much more readily.
I *think* from here, you cuold get compensated emancipation by 1836, though I'm not sure how. Also, Abigail's example pushes womens' suffrage ahead by a few decades. And, while I don't know if it's feasible for her to be named to replace her husband this early, the situation - one Senator refused, the Hartford Convention, wanting a known patriot, etc. - makes it at least possible, if only out of desperation.