You have several problems, and each of your truss designs create as many problems as they solve. The sissor truss was my first thought, but it would be expensive, and at 30 ft, beyond my abilities to design. It's just too far of a spread to know what it will take to build it.
Your other designs fail to address the spread of the walls. Tying them together is as important as keeping your pitch.
I think you have three options. The cheapest and easiest is to put in load bearing posts. The ones you have for your horse stalls would be a good location for that side of the building. Replace what you have with some 6x6's that are either in the ground deep enough for your area, or on footings that are strong enough. You'll have to determine that for your area. Put a double header on top of the posts to support your rafters and then tie the tops of the posts on either side of your RV together with a joist. Kind of like your drawing, but with posts to support it.
Your second option is to spend allot of money and put a load bearing beam across the peak of the roof. Either the length of the RV, or the full building. This will be very heavy and pricey, but it will allow you to keep your freespan. If it was me, I wouldn't do this, as it's a very big job. To support the beam, you will have to have another across your door as a header, and have the right amount of support for the load of that beam concentrated at both ends of it. Not my idea of a quick,easy solution.
My best, and probably cheapest in the end, solution is to extend your barn with a roof design for your RV, or just build another barn for it. You can do it Pole Barn style with posts in the ground wide enough to get your RV in there and put trusses over it. 16ft wide won't be that dificult to truss and I'd be you'd be money ahead building from scratch then trying to engineer something that will work in what you already have. Sometimes it's ALLOT easier,faster and safer to start from scratch.
Run the numbers, including labor, and I think you'll be suprised.
Good luck,
Eddie