At this point I'm pretty much just sitting here finding ways that I could essentially create a universe that unites several of my stories together. · 4:13am May 19th, 2017
Here's what I have so far.
Twilight Finds Herself in Generation 1. (Oldest point in Universe's history)
The events of this story have already drifted so far from the canon Gen 1 that it has caused irreversible damage to the timeline, essentially creating it's own universe that will continue to evolve on its own, and any future sequels to this story will further develop the timeline along each "generation" of MLP, until reaching Gen. 4, where each change has ultimately become a massive divergence from the canon Equestria.
Lab Horse/Space Horse
Building off of the current plans I have for "Twilight Finds Herself in Generation 1."
WARNING: SPOILERS FOR THE SEQUEL TO SPACE HORSE AHEAD!
Humans still exist, and live alongside Equestria. Over time, they began to utilize similar abilities to ponies, though are rarely able to accomplish more than basic spells. Gadget is a human (that's currently unnamed yet), but as an toddler, had somehow managed to wander into a highly experimental facility, where she is torn from the fabric of space and time and plopped down onto Earth. As a pony.
The Reality of a Shattered Rainbow/Still-yet-to-be-named-sequel to Space Horse
ADDITIONAL SPOILERS FOR THE SEQUEL TO SPACE HORSE AHEAD!
Both stories take place at the same point in time, featuring a drastically different Equestria. Here, the final effects of events from the first point of the timeline are finally shown, with humans (such as Gadget) living alongside ponies in an advanced society.
Additional stories to this universe may include a story focusing entirely off of the day-to-day functions of society, in both the primary universe, as well as an alternate universe that has a single, key, unrevealed aspect of government that differs from the rest. 
And yes, this is another one of those times where I've found myself overthinking everything over a cup of tea.
Are you sure you wanna do that? The concept of Gadget ending up in an AU is dissapointing, from a narrative build up perspective.
4538729 Don't worry. Things are gonna get rather interesting with that.
Alternatively, I could instead have two sequels.
4538733
that sounds good.
4538758 two sequels?
4538729 Though, technically going to the exact canon show wouldn't be possible, as the series starts off Lab Horse sometime in the future after the final episode of the show ends.
Because of that, Gadget would end up arriving in an Equestria some 50-something years after canon events.
4538784
one for the Gen1 story that maintains the "careening into an abyss of crazy" experience.
one for Gadget's story that keeps the "search for origin and fulfillment" experience
and let the two stories cross over, since Original Equuestria and Crazy Twilight's Kingdom are neighboring timelines, you could have Gadget successfully portal to Equestria, only to find out while living there that her real origin is in Crazy Twilight's timeline.
4538806 Thats actually pretty much the gist of it.