First class multi-dimensional arrays with natural indexing syntax would be a huge draw. You get that in Numpy, Julia, Fortran and it is extremely powerful in terms of expressing the types of operations that are common across many scientific domains.

Which shouldn't be hard since most scientific libraries rely on a standard body of Fortran code being reused underneath. The nice bits are the interactive development environment, or visual repl if you will, and Rust could reuse the efforts of Servo here to make something shiny and comfortable that is easier to get running than existing solutions on many platforms.