The first idea does have some wheels turning for me, but I must admit while I've done a lot of roleplaying within Pokemon, I've never really been one for being the pokemon. If that's a must I'll still consider it I'll just need more time to think on it. Besides that here are my thoughts around the plot that most grabbed my attention.

The ripple in time plot sounds like it could have a lot of interesting potential. I've done a lot of writing with medieval-themed pokemon before, but being several thousand years ago I'd imagine something more like proto-Phoenician. If the island is supposed to be far from human contact, if we used a world similar to our own somewhere in the very south Atlantic that could have temperate climate would give that big forest room to grow. I could expound on a number of other thoughts about locations, island geography, culture, etc. but I'd rather not get ahead of myself. The nature of time travel being linked to this island also lends to some story potential similar to Atlantis. A lost civilization, one that was able to create structures that have lasted to the modern-day, but their culture and people are completely gone.

Tempering those with a concern, the characters' language barrier seems like it could be extremely difficult to overcome, and I'm wondering what your ideas are surrounding that.

Besides that plot, I'd be happy to develop other ideas since I have a few basic ideas around for different pokemon stories. It would have the benefit of being able to develop and discuss those with you as they come along.

Also, credentials since you posted them, and it only seemed right to post some of my own. I've been doing forum RP for over a decade now. I've gotten a lot of variety in there from more traditional characters like the usual pokemon trainer and fantasy rangers to oddities like Gnar, the cave yordle from League of Legends where I used only words from his in-game language, and just niche things like a completely mute bounty hunter or a prototype iron golem-like robot. I find my average posts usually sit around 800-1k words, but can of course go longer. given this would be only two people there's less need to try and keep tempo with five others to let everyone have even input, so I'd probably shoot for around double that 1600-2k. Not specifically RP related, but I've also been writing pokemon stories for about as long as I've RP'd so I've just gotten a lot of experience developing worlds around pokemon and finding new ways to use a wide variety of the creatures.