Well, it's typical that just when you don't need it anymore (as I switched to a totally different discipline), the required functionality pops up. I found that Vol. 13 (2011) of The *Mathematica* Journal contains an article about these types of designs, [Computing Mixed-Design (Split-Plot) ANOVA](https://doi.org/doi:10.3888/tmj.13-17). I thought it good to post it here, as I know many people would love to have this.