Are there any personality theories that use the scientific method? Background

I have come across a number of personality theories. There are even disciplines of personality theories, dividing these theories according to the assumptions they are based upon. The most accepted/used theories seem to be Big 5 and Myers–Briggs Type Indicator (MBTI). However, I assume these theories use traits to determine people's personality types too.

For example, the Big 5 traits seem to be of very limited scope. Also, measuring traits like introversion and extroversion using some random questions which have polar opposite choices seems to be a fitting into a box sort of thing. There seems to be no scientific method while testing to determine whether people fall into one region or other for all the defined traits. 

By scientific determination, I mean one could use methods like the one laid out in "Cerebral Blood Flow and personality: A Positron Emission Tomography Study" to determine between, say, introversion and extroversion traits. I am not sure whether the other traits have such methods researched enough to distinguish between them.

Question


Are there any personality theories that are based purely on scientific grounds?
Are there any existing personality theories (that are being researched) that could one day be backed up by scientific research? I think the Big 5 might come under this category, but any evidence to the above regarding any theory will be appreciated. Thanks!
What you may be interested are personality traits caught by some statistical correlations, rather than 'manually' merged by an author's intuition.
One of such tools is 16 Personality Factors.

The 16 Personality Factors, measured by the 16PF Questionnaire, were derived using factor-analysis by psychologist Raymond Cattell. This article summarizes the analysis that resulted in the 16 factors and allowed the development of the questionnaire, as well as the relation between the 16 factor theory and the popular five-factor personality theory.
[...]
This statement has become known as the Lexical Hypothesis, which posits that if there is a word for a trait, it must be a real trait. Allport and Odbert utilized this hypothesis to identify personality traits by working through two of the most comprehensive dictionaries of the English language available at the time, and extracting 18,000 personality-describing words. From this gigantic list they extracted 4500 personality-describing adjectives which they considered to describe observable and relatively permanent traits.

(from Wikipedia: 16 Personality Factors and 16PF Questionnaire)