To start with my situation:
I've been a huge fan of the World of Darkness (and the new Chronicles of Darkness edition) settings for a while now, but I've rarely played it because the system's task resolution mechanic never quite worked for me. It's always felt very arbitrary to me (at low skill, success can be difficult, but once you get to a certain point it's practically guaranteed to get one success. Not to mention my players' have never liked the feel of taking dice away to represent difficulty.
(In my experience there's a pschological aspect to number of dice. Players feel empowered when they look at their character sheet and know they get a bunch of dice to roll for a skill. When you take those dice away, they tend to get annoyed. 7th Sea handles this better in my opinion because the difficulty of the task is determined largely independently of number of dice rolled. Difficulty is instead represented either through consequences, which simply requires more raises to bypass (or you just pay with wounds or narrative penalties), or through danger point use, which simply means that your dice don't go as far for the roll.)
So, I've realized that there are some similar aspects to how 7th Sea's system plays out. Both use d10 pools in which you combine a pool of skills and attributes that range from 1 to 5 in scale.
So the idea occurs to me that it could be possible to use the 7th Sea conflict resolution system within the Chronicles of Darkness ruleset. This wouldn't actually require a full use of the 7th Sea rule-set, as there are certain aspects that don't really jive with Chronicles horror gameplay. (One of the biggest reasons I'm even considering using any part of 7th Sea is because I'm planning on running Changeling the Lost, where some amount of Swashbuckling gameplay wouldn't be disruptive to the tone)
Really all I'm planning is to take most of the basic conflict resolution from 7th Sea, and adapt the merits and powers to work with this system instead. For example, instead of a merit granting 9 again on a given task, it might instead allow you to make pools with fifteen for two raises (like you can with four skill ranks in 7th Sea) This would also probably involve making willpower work more similarly to hero points as well as doing some tweaking to the health system to possibly bring some of the death spiral into it.
Is there any sort of mechanical implications that I might be missing that could cause difficulties down the line?