Erm. What?
The reason an array of size 5 (real array) "cannot" be added to the data-struct is because then there are 5 dedicated instances required for each struct, which reduces the amount of maximum structs of that type that you can have. By simply compressing that into a single variable (non-array) that extends an array of size 5 and given extended array parameters we can eliminate this limit, though then (because the way JassHelper processes things) the array references would probably (not sure here) be the same as hash-tables.