Where do you see exponential blow-up? If you replace every function in an expression tree with a tree of eml functions, that is a size increase by a constant factor. And the factor does not seem unreasonable but in the range 10 to 100.
As an example, searching for sqrt(x) would require a tree of depth ~40 which is in the trillion-parameter regime.
I think you are right, each node in some other expression tree formed of primitives in some set Prim would be increased by at most max(nodes(expr)) for expr in Prim.
That's essentially what the EML compiler is doing from what I understand.
For extreme regularization, one can even go down to 10 arbitrary precision numbers: if we have a single vector of 10 dimensions, we can re-order the components 10! different ways.
10! = 3 628 800
so we can retrieve ~3M vectors from it, and we can form about 10 T inner products.