Connected components of Hurwitz schemes and Malle's conjecture

Let Z(X) be the number of degree-n extensions of Fq(t) with some specified Galois group and with discriminant bounded by X. The problem of computing the asymptotics for Z(X) can be related to a problem of counting Fq-rational points on certain Hurwitz spaces. Ellenberg and Venkatesh used this idea to develop a heuristic for the asymptotic behavior of Z0(X), the number of - geometrically connected - extensions, and showed that this agrees with the conjectures of Malle for function fields. We extend Ellenberg-Venkatesh's argument to handle the more complicated case of covers of P1 which may not be geometrically connected, and show that the resulting heuristic suggests a natural modification to Malle's conjecture which avoids the counterexamples, due to Klüners, to the original conjecture.