Snap was my favorite Pokemon game aside from the main games. So it would be an understatement if I said I've been thinking of ideas for a sequel for over a decade.
For the ideas in the OP, my thoughts:
1. Definitely agree on the need for more Pokemon, and Pokemon from newer generations. One of the major downfalls of the original game, besides it's overall length, was that there weren't many different breeds in the game compared to the 151 available.
2. That's an interesting idea, especially since certain Pokemon are only found in certain regions. However, it would be hard to distinguish a water level in one region from another - water/oceans in the main games are very similar. Of course that's where imagination comes in. As for "long levels", I'm not too big on that. One of the best parts of Snap was the appropriate length of each level and the challenge of being limited to 60 snaps a level. Keeping the levels relatively short is the right move to not scare players into taking photos because they are worried about running out.
Also, for example: If I'm missing Charizard on the Volcano level, I have to wait all the way until the end of the level to snap him. Even with the speed bost upgrade it takes a while, especially when I'm doing the run solely for Charizard. If the levels were super long in Pokemon Snap 2, it would be terribly annoying to re-run through the levels.
3. I like this concept, and it was pretty much like this in the original game:
Beach - None
Tunnel - Zapdos
Volcano - Moltres
River - None
Cave - Articuno
Valley - Dragonite
Rainbow Cloud - Mew
Of course Gen 1 had a limited stock of Legendary Pokemon, so it wouldn't be a change to incorporate Legendaries
4. Makes sense. The game needs to cater to the casual fans as well.
6. Seems a bit aggressive. This isn't the main series with die-hard fans waiting for each release, 1 version of the game is probably sufficient. Besides, I can't think of many game series' that aren't Pokemon that release multiple games at the same time. If you want multiple versions, I'd suggest one being the sequel to the other. This would help in exposure and sales. Even 1 year apart is ideal.
7. That sounds really fun. The way I envision the game, however (see below), it may be hard.
So my ideas/suggestions:
- 2 player mode. Both cooperative mode (work together snapping pics for the professor), and battle mode (battle against each other to get the higher score that level).
- More "upgrades". Expand on the apple, pester ball, pokeflute. There should be several more items and tools to use. Since buttons are limited, one button should open the item menu then you select what you want to use from there.
- More novelty shots (i.e. Surfing Pikachu, Singing Jigglpuff), perhaps an undefined/unlimited amount. See next point:
- Interaction between Pokemon, and on that note, a smarter game interface. If the player gets a Skitty to cuddle with a Houndour for example, the game notices that and awards points.
- Different difficulty levels (more pictures per level in easier modes, more leniency in having the Pokemon in the center of the frame in easier modes, etc.)
- NPC characters! For example: Youngster Joey wants a picture of a Rattata, or Mr. Briney lost his Wingull and wants the player to take a picture of it's last known location. Stuff like that.
- More complex system to rate pictures. In the original game, it was known what the max score on most - if not all Pokemon - was. By making it more complex, it urges people to keep playing.
- REPLAY VALUE!!! The biggest issue in the original game was that once you were done the game, you really didn't want to start over, since it's the same thing over again. So how do we increase replay value? Maybe you get to choose a starting Pokemon and each one has a special ability you can use once per level. Maybe Bulbasaur can use Vine Whip to "freeze" a Pokemon in place for 5 seconds while you attempt to get the perfect shot. Or Togepi uses attract to bring Pokemon closer to the player. Maybe adding in side quests, specific novelty shots that actually require time to get.
- Make each level impossible to be completed in one run. In the original game, each time you restarted a level, everything restarted - the Pokemon, triggers, etc. Maybe have certain parts on each level where you gain progress in something and have to keep playing the level to continue that progress. Like maybe a Vulpix is trapped under boulders and you have to get rid of those boulders to get a picture of it. And it's impossible to free the Vulpix in one run, for whatever reason. Maybe also incorporate detours on some of the levels. I kind of envision it like on the Beach level, you could maybe have the option to move to the shore of the water for better Lapras shots.
- Have many Pokemon feature on different levels. In the original, I think Pikachu was the only Pokemon that could be snapped on different levels.
- Expand on the "Pokemon Signs" concept
I have many more ideas but I think this is already enough to grasp for now.