We would expect that the FTO is very much SOLID in their ability to be a Paramedic or EMT. You can expect that someone that is an FTO is essentially the "model employee" and "model EMT or Paramedic." In short, the FTO know their stuff very, very well and you don't generally have to worry about that employee from a "clinical" perspective. Here's the difficult part about being a good FTO. In that role, you have to be able to teach and be able to figure out your trainee's learning style and be able to ensure that your trainee learns. Over the years, I have met some people that were absolutely spectacularly good at their job. Many of them wanted to be an FTO because, let's face it, it looks good on a resume. A very few of them could teach others effectively.
At the core, an FTO is a teacher. If you don't feel like you're ready to take on a teaching role, then you're not ready to be an FTO. We all want to jump in and just do things because we know we can do it better and faster than the new guy... but if we do that, they don't learn. So FTOs have to know when to step in and step back to let their trainee learn. As an FTO, you also have to learn to model the behaviors you want your trainee to emulate both on calls and between calls. You're responsible for enculturating your trainee into your company. You're the guide. You're their resource. You're the one that sets the boundaries for what's acceptable and what's not acceptable.
Is it possible to become an FTO at a company where you've never worked before? Yes. Does it cause issues when the company hires external applicants into that role? Yes. There's a reason why FTO candidates are drawn from an internal employee population that's established and has been there for a couple of years. They embody the culture of the company. An "outsider" doesn't know the culture.
If you truly want to become an FTO, I suggest you take a course in adult teaching. It will give you some very valuable insights into how adults learn... and insights into various styles of learning. Such a course will also help you be able to teach someone more effectively because you'll learn how to figure out how someone learns best. Teaching is a skill. Very few people are natural teachers. The material you're teaching doesn't matter; it's learning how to teach that is important.
Becoming a Supervisor is a LOT like being an FTO because your job encompasses teaching. It also requires the ability to lead a group of people, to know how to take command and how to relinquish it. Supervisor is often the first level manager in a company because you usually have some disciplinary authority. You may have limited budgetary authority or some scheduling authority. Sometimes it means you have to be able to take a step back from doing direct patient care, even though you may be on scene. Also, once you become a Supervisor, your relationships among people that were formerly your peers will change. An FTO can still be a peer, but a Supervisor is in a whole different group of people with a different dynamic. Depending upon setup, you may also be responsible for various aspects of company operations.
FTO is a good gig... Supervisor can tear your hair out. I know...