A lot of the HBS game ended up becoming canon with the House Arano sourcebook. The sourcebook has 8 mentions of Herotitus in it's pages and some of the changes to that world in the game's expansions would not be noted- like becoming a Black Market world. Or at least I THINK it ended up with one, I do not have the in-game map up at this time. Panzyr and Weldry both have bits in their entries mentioning that the first one has seen a drop in transit traffic to Herotitus while the second has maintained or maybe increased their transit traffic.
TTS Herotitus mentions the New Hedon's pleasure circus like capital attracted a black market, so either way one is present and was likely what drew the merc trade since it would easily be considered a great place to stop for some R&R. Such a establishment might also attract pirates for much the same reason with a air of Port Royal.
As part of the establishment of the mercenary trade on Herotitus, it would be the ideal place for the representatives from the 5 Houses (like Lady Cunningham-Davion), MoC & TC from HBS to set up shop as their governments' merc liaisons. I mean the Kuritan merc liaison pretty much seems to fall into the New Hedon camp already. The HPG would allow them to receive orders as well as be a good intelligence station for the Houses, regional powers, and of course ComStar's ROM. From Herotitus they could find merc groups that would be able to carry out any military actions needed to represent their nation's interests- like one of the Flashpoints about the Dracs wanting to deal with a FedSuns officer.
The military market on Herotitus would also be a good outlet for what Mechdur could produce in the way of infantry weapons, armored vehicles, munitions, and any IndiMech conversion kits. Same for Detroit's military production as small as it might have been at the time.