What is CC? I'm not sure what OP means either, I'm guessing...overpowered?
Anyway, I don't think it would turn him into an amazing character (or 'kit', lol). I don't use sabotage on this guy, I consider it a worthless power on him (it's great on the turian engineer though), especially when you have tactical scan, which is really nice. I'm a big fan on tactical scan, even though it can only be used on single targets, it still gives you a really decent damage boost.
Arc grenades wouldn't synergise with any of his other powers. The reason why arc grenades are amazing on the quarian engineer is because of incinerate. Arc grenades on their own are kind of meh, unless you're playing a demolisher who has access to a ton of grenades, but even then, they're not exactly amazing.
Right now, I can't think of any other power which could serve as a decent replacement in place of sabotage.
I'm not a big fan of the quarian marksman. I know this isn't a thread for comparing characters, but why use the quarian marksman when you have the turian marksman (better weapon damage, stability bonus, better health and shields)? The turian is superior in every way, in my opinion.
They really failed miserably with the quarian marksman, he's such a badly implemented character (or 'kit', lol). I just don't get this character.