Have option for individual practice tests for each section. (i.e. have one for the writing section)

I heartily concur... perhaps it would be beneficial to be able to take sections in the order you desire (for example, you want to focus on the Writing and Language section that day, or you do not have access to a calculator, but wanted to practice a Math section without having to take the two prior sections as well).

I agree! With super scoring nowadays, a lot of students only need to focus on one section of the test. For example, I'm done with the math portion. I'm happy with my score. Now, I'm only studying for the reading and writing. So, I only do half of the practice exams. However, Khan Academy doesn't count it as taking a practice exam, so the practice it gives me every day does not adapt to how I'm doing.