I would not worry at all about skill points right now. As stated, you get a free re-spec at every level, you might even get a couple bonus ones if I remember right for every 100 days subsribed. You will easily have at least 6 respecs by the time you hit max rank. IMO the best course is to just put skills in to whatever you feel is right, until you hit level cap, and then you have at least 6 free tries to modify your final build, once you have grown to understand which bridge officer skills work best for you.
As for builds, there are plenty of examples floating around, especially in the sci ship part of the forum rather than the sci officer part.
I agree with the poster who says cross class are not weakened, but can actually be quite effective. I have an Eng in a Sci ship that I adore using. He has much more survivability than my other sci/sci and is more of a crowd control/APC (not quite a tank, but heavier than a standard sci) than anything else, which I really enjoy playing.
Sci/Escort is a build I have seen a fair bit, and from what I've seen, can be very deadly indeed. But it is not what you would call a CC build. There just aren't the sci boffs slots available. The MVAM as mentioned is an exception, as is the BOP, but they are still limited in CC, and usually either use the extra sci slot for Photonic Shockwave, esp on BOPS, or Transfer Shield Strength, esp on MVAMs.
Personally. I prefer to just run a proper CC build on a Sci/Sci when i fancy CC, and switch over to my Tac/Escort when I need a DPS fix. And then my Eng/Sci if...etc etc..I would wager most of us have a fair few toons