It's a shame they never brought Maxwell back for Ds9. Would have been cool to see O'brien break him out of a prison, or even just get some valuable insight from him, and allow him a chance to redeem himself in some way.
A wonderfully talented actor like Bob Gunton, playing such an interesting and layered character like Ben Maxwell... A character that just so happens to be incredibly relevant to DS9's overall story... AND one of O'brien's closest comrades.. Huge missed opportunity.