Ok from my initial brainstorm there are several things I want to bring up.
Me: I have never run a dark heresy campaign and I have never had to design an in depth (plots within plots) game. While I am sure I can do it there may be a learning curve involved and it would clash with my improv style of GM’ing. I can pull it off but there may be a delay between the decision to start campaign and the actual start as I work through how I will tackle running it. The biggest problem I see is making it possible to find all the threads that are inter-twined. I can make very intricate plots and conflicting character ambitions but they may be for the most part lost on you as they may be so deeply hidden under layers of deception that they are hard to find.
What I am saying is that as a rookie GM there is going to have to be a rigorous amount of feedback if you are not liking the campaign as that will allow me to adjust to find the right levels for all the variables involved. [ I have however read all Eisenhorn and Ravenor books so I do have a base of knowledge ]
Linked Campaign: Having two campaigns not only linked by general lore and back-story but that affect each other introduces several elements:
1. Players from one game affecting the other, if we have all the same players in both campaigns this is less of an issue. There is the possibility if we don’t have all the same players that someone may be annoyed that a player in a different campaign is impacting their character.
2. What you learn in one campaign could be useful to know in the other and you may be tempted to use that knowledge to gain an advantage. That is meta gaming and if we do go ahead with the 2nd campaign that would be a big no-no. If through roleplay and reasonable means that knowledge is passed between the two campaigns or is common knowledge then of course it is fine to use that info.
3. Decisions by characters in one campaign shouldn’t change the internal group attitudes in the other campaign. Just because you dislike a character or two characters clash in one campaign those feelings should not transfer to the other campaign. [ie: Be mature]
Style of Campaign: What kind of Ascension campaign do you want?
1. Do you want a tightly entwined story that heavily relates and impacts with the Deathwatch campaign or a more loose one taking place in the same area/enjoying the same back-story and major events but largely not affecting each other?
2. Do you want to start from scratch as a newly elevated Inquisitor, start half way through a scratch built inquisitor’s career or I provide an Inquisitor that I was going to use as a NPC (largely requiring you to adopt that character’s viewpoint and thus reducing the group’s freedom).
3. How much combat? In deathwatch we fight every session, however, dark heresy is about intrigue, investigation, conspiracy and usually ends with eventual damnation or death at the hands of those you hunt. Therefore do you want me to focus heavily on the non-combat elements in the Ascension campaign or make it a more a even combat/non-combat campaign?
4. An Inquisitor has a certain level of freedom a Battle Brother does not. While they do have duties to uphold, an Inquisitor can move freely throughout the Imperium without being impeded or being thought of betraying their remit. Thus the opportunity for a sandbox style campaign is more available here. Do you want a sandbox campaign or a similar linear (with effects, twists and turns being caused by your own actions) style to deathwatch?
5. Ordo Xenos. This is the ordo that is most easily integrated with a deathwatch campaign for obvious reasons. Inquisitors battle all threats though so an Inquisitor from a different Ordo is possible. You will have to weigh what foes you wish to face and the level of integration between the two campaigns in this decision.
Cast, Crew and Cameos: Having the game take place in the same space can lead to characters appearing in each others campaign both in name and in real terms.
1. How much of the current and future cast of deathwatch do you want appearing in the second campaign and vica versa?
2. Do you want the BBEG’s from one campaign to appear in another, make cameo appearances or outright be the same BBEG’s but are being hunted by two different organisations?