Well basically this is not a new kind of game, rather a very old one - I played a couple of such RPGs back in the 90s and they have an unbelievable charm. They are basically "3-engine RPGs": a more or less advanced 3D FPS engine for travelling in the world, an isometric battle module and a 2D engine that's used for conversations, shopping, inventory etc. - and also for depicting the inside of buildings. Betrayal in Antara is a prime example for this type of RPG, you can download the demo at <!-- m --><a class="postlink" href="http://www.pcgameworld.com/details.php/id/1657/">http://www.pcgameworld.com/details.php/id/1657/</a><!-- m --> . Please download the demo and take a look at it, since in what I'm saying after this point I assume you know how BIA basically works.
The biggest advantages for a team like ours in making such a game is that it lives mostly from 2D graphics, and mapping is a lot faster than for an FPS. With the amount of time you spend on a very detailed building in an FPS, especially in modern engines, with this amount of work you can build a whole town in such an RPG engine, since none of the houses (or only a few of the larger ones) have any interior, most of the time you just click on the house and a dialogue box pops up.
Such a greatly simplified (but still not oversimplified) 3D environment allows one very important thing that can't be achieved in an FPS with acceptable expenditure: the seamlessly connected, immense world you can travel from one end to another and interact with it. Thanks to the fact that buildings are relatively low-detail and no monsters are running around in the map, the engine can deliver a lot more punch with the same computer, like real big maps (meaning you need to cross from one map to another less frequently, making gameplay smoother and further decreasing the time spent on mapping, since less map parts need to be duplicated).
While especially 6 years ago Antara's 3D world was breathtakingly beautiful, it could be even better with Vavoom. This time, the waterfall would really flow and the water would be translucent, and the wind might sway the branches of the trees and this afternoon it might be sunnier than yesterday, next morning it might rain etc. etc.
Also, the fact that the isometric battle module would be based on a 3D engine would allow a lot of extra things too that wasn't possible back in the mid-90s.
Some of the Korax' Heritage ideas might be easier to realize here than in other (FPS) projects - things like weather influences, a mouse-based GUI, a complex inventory system etc.
I know Mago would be with me on such a project, I'm not sure about the others. At any rate, this project surely wouldn't start now, but rather when work on the current projects is more or less finished (that's why I didn't even mention this idea this far though I had it for over a year now).