Taking courses at WGU not part of my degree program? And credit by examination

[sciencemathematics1]

What if I started working on one program, finished all of the courses that I wanted to take in that program, and then switched majors or transferred elsewhere?

Yes, you could do that but like ss20ts mentioned, it is not really worth it. You're better off just taking those courses from an outside provider like Straighterline or Study.com, or take them from a local community college or something if you prefer.

If you really wanted to do this you'd have to jump through some hoops...

https://www.wgu.edu/online-teaching-degr...admissions

It doesn't seem like there are many entrance requirements from this page that I wouldn't already have. It says that I have to take a certain exam "either prior to admission or before beginning the Foundations of Teaching subject area once you are in your WGU program", but that is all that is required.
The courses that I want to take are not ones that are found on study.com or straightliner. I would rather be able to take these courses online in a competency-based or self paced format.
There are online courses elsewhere for these math courses but they are very expensive. I also prefer the competency-based model of WGU.
I am mainly interested in the mathematics courses available.
https://www.wgu.edu/online-teaching-degr...ogram.html
https://www.wgu.edu/content/dam/western-.../BSMES.pdf
There are about 5-6 courses that I want to take.
Probability and Statistics I 
Probability and Statistics II
Linear Algebra 
Abstract Algebra 
Advanced Calculus 
Calculus III 
I am also considering the following courses, but am not sure if I want to take them.
Mathematical Modeling and Applications
Mathematics: Content Knowledge.

I already completed Calculus I and II from AP exams, so I can take other courses. getting credit for these courses, would I be able to skip College Geometry, and Trigonometry/Precalculus? This also qualifies me for entry requirements into the CS program, and it would fulfill the prerequisite for taking further courses. 

I am considering having these courses completed so that I can transfer them to TESU and make them part of a degree program for the BA in mathematics.

If I went there with my general education requirements already completed, then it would just be the teaching classes that I would have to skip over.
Or, I could just complete the general education classes with them. Since its competency-based, I can finish them quicker.
The obstacle which concerns me most would be if my mentor would allow me to take the courses in the order I want to take them in. 
I have asked about this when it comes to the computer science program, and I was told that I could take courses in the order that I wanted to take them in as long as I would complete prerequisites for courses and I completed the more advanced courses afterwards.
I am thinking that I could progress through these specific courses as it is normally outlined that they are progressed in, but skipping the educational teaching classes.

It would be fine with me if I had to pay for two terms at WGU. These courses would end up being just as if not more expensive if I took them elsewhere. It is also fine with me if I had extra time between the two terms, as I could just use that time for studying computer science which would help megetthrough the CS program faster when I enroll.

I could just withdraw entirely after completing these courses, although I am not sure how smoothly the process would go for this or for changing majors.
I also looked at the physics and chemistry programs that they have.