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 up. I found that Vol. 13 (2011) of The Mathematica Journal contains an article about these types of designs, Computing Mixed-Design (Split-Plot) ANOVAComputing Mixed-Design (Split-Plot) ANOVA. I thought it good to post it here, as I know many people would love to have this.