The Force
The force can be used for anything, it's all encompassing energy that connects all living things in the Star Wars universe.
Could somebody use the force to help them mow the lawn?
Yes, yes they could.
- Ezra Bridger has a natural ability to connect with animals and is an incredibly talented pickpocket.
- Luke Skywalker was a natural pilot with no form of training but could fly fighter ships with ease.
- Rey has the same ability as does Anakin Skywalker who was also mechanical genius.
Some Legends examples would include:
- Revan who is capable of understanding any language in the galaxy.
There are also species in the Star Wars Universe who are all force sensitive by default. Like the Sith species and the Miralukans in Legends.
Species
As far as a species with natural learning ability but not force sensitive I'm not sure what you mean. Every species is typically good at something.
However in the Star Wars universe you will find that most Force Sensitives are particularly naturally talented at certain things.
There are also species in the Star Wars Universe who are all force sensitive by default. Like the Sith species and the Miralukans in Legends.
- Green Sabers were for Jedi Consulars
- Blue Sabers were for Jedi Guardians
- Yellow Sabers were for Jedi Sentinels
If you want to make a unique saber for your fanfiction I would suggest google searching "unique light sabers" so you can get a feel for what unique ones already exist. You can also google search "Make a custom lightsaber online" and usually find a couple of sites that allow you to make your own unique saber by picking each and every individual part. It is very helpful and I have spent hours on it for my own Fanfiction.
It is entirely possible for somebody to go from the light side to the dark and back again and back again and so on. Many Jedi and Sith have changed their allegiances multiple times both in Canon and Legends.
It is also important to understand that it is not just light or dark, there is the gray in the middle, in Legends there are Gray Jedi who believe in balance of Light and Dark and started their own order.
There is also just the idea of the middle of the two or the Bendu which has now been canonized as well.
Honestly just go through Wookieepedia the star wars wiki, it has everything Star Wars in it and even allows you to search by Canon or Legends, it is literally a life saver and has everything you will ever need for a fanfiction. Bookmark it and explore it like a bible, it has everything from family trees to relationship webs to ship schematics and deck plans of almost every ship to ever exist in the Star Wars universe.
Also another incredibly useful source to use is the Star Wars galaxy map which will give you a good idea of where everything is in the galaxy. All of the worlds listed in the map will have entries in the Star Wars wiki as well.