i feel i will say some things first, this is all my and a team member's ideas and are concepts and not concrete yet. this mechanics and plot ideas.
So the game as you may not tell is based around RBY & GSC. It is after GSC and 10 years later The concept characters (second up today) show each region off. you begin your adventure in either johto or kanto and just like every game you collect badges. up to the seventh gym there is a disturbance and the sevii islands attract a new island out of nowhere. the sevii island are then taken over by these unknown pokemon. you head out to the sevii islands and eventually onto the new island ... the island is guarded by three guardians and the island is infact a enormous pokemon ( uncapturable to help the game run better)
the enemies of the game our old ex- admins of team rocket and have brainwashed the opposite regions gym leaders. you must defeat the gym leaders, and the admins and prove yourself to the guardians. you can then head home and beat the eighth gym and become the new champion. you can head between the two regions and the sevii island and possible the enormous island.
So this was my original idea... but i felt just to focus on the new island and the sevii islands... for reasons to help me in life and not to be in eternal debt...
Some mechanics is a level weight system in flying, riding and surfing. large pokemon and lighter pokemon in a level above 20 can fly you around safely and the fl will basically be open world but an area you have not unlocked yet will end up with you being sent back to when you began flying. lighter and medium sized pokemon can allow you to ride on them past level 25. when surfing light and large pokemon allow you to surf on them. and pokemon above level 40 only. if a pokemon that knows surf is too heavy it will dive underwater. and it will only do this past level 45. light pokemon past level 50 that can surf will be able to ride waterfalls. a mechanic a fan game introduced to me is any fighting type move can break rocks instead of just rock smash. also only pokemon with high attack and or special attack above 50 can move large boulders and scale rocks. also any thunder type or fire type can light up a cave like flash. because of these mechanics, only hm surf and fly remain that are useful.