By restricting our own freedom, we gain collective power. It's a tenet of larger society, but also scientific society.
For some the restriction is in the form of Arabidopsis. Zea for others. Populus, Lotus, Medicago...the list of model organisms that are used to answer fundamental questions about the genetics of plants goes on.
But what about the evolution of plants? To a degree, we can compare the genomes of model organisms to hint at some of the broader evolutionary patterns. But evolutionary patterns are generally derived by comparison with multiple members of a single clade. If one wanted to understand the evolutionary patterns of grass, we couldn't just look at a single model organism. We would need to look at a model set of species.
What would a model species set for grasses look like? It would have to be large enough to cover the major clades (~10), but restricted enough that researchers could measure standardized metrics on every species. Probably about 100 species. For grasses, they should come from different continents, span multiple origins of C3 and C4, and cover a wide range of environmental tolerances. Seed should be readily accessible. Most likely seed sets would have to be collected by a central agency for distribution to willing researchers. A central database would be needed to store all the data for other researchers to use.
Once that happened, an individual researcher that was interested in the cold tolerance of grasses could grow up all 100 species, measure their cold tolerance, and then examine the evolutionary patterns of cold tolerance. The next researcher that wanted to examine stomatal density could do the same, and then would be able to compare it with cold tolerance. Root anatomy, mycorrhizal dependence, genome size, carbonic anhydrase activity, flowering phenology, drought tolerance...the database would build. Each time we would learn more about multivariate trait selection in ways that no one lab could do.
Why doesn't this exist? Hard to say. Part of it is probably some small group just deciding which 100 species to use. Would it be perfect and cover all the potential evolutionary questions? No, but there are researchers that are asking these questions anyways, so they might as well be using the same species. Plus, there always could be a second species set identified to fill the gaps in the first for a second round of measurement.
Why not just keep a database and let researchers work on whatever species they felt best allowed them to examine specific ecological and evolutionary contrasts? Never enough overlap. Brassicaceae has 3700 species and even the Arabidopsis genus has 9 species. But everyone works on thaliana even if other crucifers might be better to answer some questions.
Once the scientific community agrees to encourage the restriction of freedom of inquiry into plant evolution a little more, a large amount of collective power will be realized. How long should it take? A few informed individuals who are not afraid to make political sausage would need to be in the same room for about 2 days. How long will it take to get people in a room for 2 days? Hopefully within a year or two.