Consider declarations in a model:
typedef int[1, 10] id_t;
clock x[id_t];

Then the following works:
E[<=1; 1000] (max: x[1])

But the next one does not:
E[<=1; 1000] (max: (x[1]+x[2]))

Also it would be nice to handle other expressions like:
E[<=1; 1000] (max: sum(i:id_t) x[i])


And:
E[<=1; 1000] (max: random(3.14))

Lifting this restriction would allow designing custom distributions via experimentation.