I don’t care where you put your hands, up, down, just don’t elbow me in the face in the process!!!
Ride photos are hit or miss, with or without hands. It doesn’t seem practical or reasonable to ask others to change when in the end, it isn’t going to fix the problem.
I think with thrill rides, there is a certain expectation that people are going to hold up their hands, especially at the drop parts which is where the photo is usually taken on many rides. So asking people to go against the norm seems a little much to me. If this was not the norm or expected behavior, it would be different. IE, asking people not to hold their hands above their head in a show is completely reasonable because no one expects the person in front of them to put their hands up. On a coaster, I expect the people around me to either be holding on for dear life or raising their hands.
Putting them down for the pic sounds like a good compromise until you stop to really think about. Many people don’t know when the flash will be, it is usually at a part of the ride you’d traditionally raise your arms at (even if you’d had them down up to that point), it can be difficult and/or distracting trying to pay attention to when and where you’d need to lower them, with many people not being able to react fast enough even if they genuinely tried, and this would impact / inconvenience the majority not the minority.
Now, let’s factor in that just as many photos are “ruined” by other things besides arms, people’s heads, seat backs, hats, Mickey ears, and even if you aren’t blocked by anything, that still doesn’t guarantee a good pic. You could be looking the wrong way, or have your eyes closed, or be making a weird face. It’s a gamble no matter what.
So in the end, if keeping hands down, would actually make a difference, and if riding with hands down was the norm, I think it would be reasonable to ask people to do that. However, that just isn’t the case, so I don’t think choosing to keep your hands up is inconsiderate at all.
It’s definitely great to point out the issue and make newbies aware of something they might not have considered. Knowing the risk of not ending up with great pics or pics where you are blocked could help someone decide if paying for the package is worth it or not.
If capturing the ride memory is important to you, try something different. Pose outside the ride or even in the queue line. The backgrounds for those pics will be much better themed, and you can take time to get a good shot, everyone posed, smiling, looking at camera. If there is a test seat or sample ride vehicle you could pose there. Ask to ride in the front row or ask the opinion on which rows or seats will provide the best angled views. You can always look at other’s photos before you ride to see the camera angels, and where you need to sit or look for the best photo. Be prepared to ride more than once to get that perfect shot. But most of all, just realize there is no guarantee on the quality of the ride photo. It’s a candid shot and any number of things could mess it up, so I wouldn’t depend on that alone for your ride memory.