I found a paper [1] containing a factor analysis of how various "personality facets" relates to the underlying Big Five personality traits Neuroticism, Extraversion, Openness, Agreeableness and Conscientiousness. These underlying personality traits have been found to remain relatively constant over time, and they are only five. In summary: it seems that many facets of personality can be explained from just five values of these underlying traits. The paper provides an empirical matrix explaining the general relationship between them: \begin{array}{lccccc} \hline Facets & N & E & O & A & C \\ \hline Anxiety & +0.80 & -0.09 & +0.05 & -0.01 & -0.03 \\ Angry hostility & +0.64 & +0.02 & -0.04 & -0.49 & -0.02 \\ Depression & +0.77 & -0.15 & -0.00 & -0.04 & -0.20 \\ Self-consciousness & +0.75 & -0.22 & +0.08 & +0.04 & -0.07 \\ Impulsiveness & +0.48 & +0.47 & +0.11 & -0.25 & -0.15 \\ Vulnerability & +0.67 & -0.14 & -0.16 & +0.11 & -0.40 \\ \hline Warmth & -0.21 & +0.57 & +0.26 & +0.46 & +0.09 \\ Gregariousness & -0.22 & +0.69 & -0.01 & +0.19 & +0.01 \\ Assertiveness & -0.27 & +0.52 & +0.17 & -0.31 & +0.43 \\ Activity & +0.00 & +0.49 & +0.18 & -0.20 & +0.58 \\ Excitement seeking & -0.12 & +0.63 & +0.10 & -0.22 & -0.05 \\ Positive emotions & -0.22 & +0.58 & +0.37 & +0.23 & +0.17 \\ \hline Fantasy & +0.02 & +0.13 & +0.66 & -0.24 & -0.12 \\ Aesthetics & +0.08 & -0.08 & +0.68 & +0.23 & +0.02 \\ Feelings & +0.21 & +0.18 & +0.68 & +0.01 & +0.26 \\ Actions & -0.13 & +0.28 & +0.57 & +0.17 & -0.07 \\ Ideas & -0.17 & +0.01 & +0.69 & -0.13 & +0.08 \\ Values & -0.06 & +0.08 & +0.63 & -0.03 & -0.10 \\ \hline Trust & -0.27 & +0.25 & +0.10 & +0.57 & +0.14 \\ Straightforwardness & -0.03 & -0.11 & -0.15 & +0.68 & +0.02 \\ Altruism & -0.14 & +0.26 & +0.06 & +0.63 & +0.34 \\ Compliance & -0.13 & -0.20 & -0.02 & +0.77 & +0.00 \\ Modesty & +0.15 & -0.23 & -0.12 & +0.56 & -0.13 \\ Tender-mindedness & +0.17 & +0.11 & +0.18 & +0.66 & +0.08 \\ \hline Competence & -0.41 & +0.01 & +0.17 & +0.03 & +0.67 \\ Order & +0.11 & -0.09 & -0.16 & +0.11 & +0.66 \\ Dutifulness & -0.17 & -0.06 & -0.14 & +0.32 & +0.67 \\ Achievement striving & -0.05 & +0.14 & +0.07 & -0.09 & +0.77 \\ Self-discipline & -0.33 & -0.07 & -0.02 & +0.11 & +0.75 \\ Deliberation & -0.19 & -0.48 & -0.01 & +0.21 & +0.40 \\ \hline \end{array} Starting with five random traits (in a vector $t$) and letting the matrix above be $W$, we can produce 30 facets $q$ with $q=Wt$. Generating some personality facets this way and making them feel attraction/repulsion towards each other (based on how similar their personalities are) gives an interesting simulation.
The felt force on each unit with respect to each other unit is calculated with the vector form of Coulomb's law $$F=\frac{q_i q_j}{|r_{ij}|^2}\hat{r}_{ji}$$ which gives the major behaviour. Additionally to this, there are some minor behaviours: A strong repelling force if bumping into each other, a weak force that tries to keep them in the middle of the screen and a weak (extra) force towards the most similar unit (which I thought might be a crude way to add a "conscious choice" to the units in the simulation rather than only letting them follow insticts).