Man they are such lovely models, be a real shame not to use them... I used to lurve my hellions in the old codex using the Baron, real infantry killers and scoring made them useful indeed... I always used to run the Helliarch with an agoniser back then to assist the Baron in CC, using Hit n Run to frustrate the enemy.
Maybe run a plain helliarch now, to escort the reaver spam and give them some poison firepower support would be useful?