  Semi-inclusive processes are very promising to investigate $XYZ$ hadrons at
the next generation of electron-hadron facilities, because they generally boast
higher cross sections. We extend our formalism of exclusive photoproduction to
semi-inclusive final states. The inclusive production cross sections for
charged axial-vector $Z$ states from pion exchange are predicted. We isolate
the contribution of $\Delta$ resonances at small missing mass. Production near
threshold is shown to be enhanced roughly by a factor of two compared to the
exclusive reaction. We benchmark the model with data of semi-inclusive
$b_1^\pm$ production.
