In the Fabulous Destiny of Galaxies, day one, two speakers (Devriendt and Ellison) mentioned the issue that detailed chemical abundances are some kind of integral of the star-formation history (a pretty complicated one if you think about it). This brought up two ideas. The first is that the luminosity is also some kind of integral; it would be interesting to ask about what aspects of star-formation history have very different impacts on the two different integrals. There are really many different integrals, because you can look at any element, and you can measure the luminosity in any band.
Two other speakers (Yi and Fontana, I think) mentioned the fact that semi-analytic models (and, presumably, simulations) are unable to make massive galaxies as old and dead, on average, as they are observed; indeed all models produce a significant population of blue, very massive galaxies (which are never observed in the local Universe).