Have a surface that reacts exactly like grass. They don’t use rubber pellets but some type of ground cork, clay, and sand that reacts like dirt. I am not sure what studies have been done with football. AstroPlay Cool turf is made with heat resistant fibers but is still the same rubber pellet system.
Ideally a surface that doesn’t absorb heat or cause rug burns coupled with infill that behaves like dirt is the ultimate goal. I think it gets there in the next ten years.