Myself and Linkandzelda are making one called Platinum Origins, but it is only in the very early stages of production, nowhere near ready for any sort of release or even a preview.
Sounds good and I would definitely be willing to play it, but it seems as if that would be extremely challenging to make. Custom sprites for all the 4th gen pokemon, all of the new moves, plus animations for those moves? Whoo, boy... But you could probably manage it (It would take a few years, of course). After all, you guys already have the physical/special split working in LC, so that's one thing out of the way. I would imagine that the Poketch from D/P/Pt would not be included, but that's fine, as most of the functions were largely superficial anyway. The Pokenav was much better IMO.
Since you were able to put both Johto and Kanto in this one, wouldn't you be able to put Hoenn into Platinum Origins? (I seem to hear a LOT of people asking about whether Hoenn is in Liquid Crystal which, naturally, it isn't.) It would be interesting to revisit Hoenn and see how it has changed in the years following the story. Perhaps it has undergone some rapid growth and thus some places (like Slateport) are now large cities. The Battle Frontier also presents an excellent opportunity to fight legendary trainers from the pokemon universe, such as Red from Gen1, Steven from Gen3, or even Yellow or Ruby from the Pokemon manga. There are a lot of possibilities. Of course, if you decided to do this, then it'd be easier if you were using a R/S/E rom. Doing that would make both Liquid Crystal and Platinum Origins THE definitive "main story remake" pokemon hacks out there.
Anyway, I'm not saying you have to do this, or even that you have to make it in the first place. Who knows? You might get tired of making Pokemon hacks along the way or maybe have too many demands on your time. Happens all the time.
But the main thing now is to finish LC, right? A few minor touch-ups here and there, the inclusion of the pokegear, and you've pretty much got a finished product.
Great work so far, though! Can't wait to see what you guys will cook up next!