An RPG with emphasis on dialog (or at least the choice for the emphasis to be on dialog). We should have a party rather than a single character, but you should focus on a few very deep characters instead of many less-nuanced ones. Make our choices matter, and make us care about our characters. All of them.
I'd personally prefer to see an original IP, but tagging something with Planescape regardless of whether it's a sequel or spiritual successor would likely bring in the most support, and I would of course support that as well. I have no idea who has licenses to what, so obviously it'd be a judgment call as to whether or not the extra support would be enough to justify using the name/setting.
I'd love to see you go completely off the rails in creating a new IP, doing something that would never occur to most of us here, and would never get green-lighted by a publisher. However, if you're going to do this, consider getting a least a concept before starting the kickstarter project.
My favorite type of combat is the real-time, but pause-able type from the Infinity Engine. But any type of very strategic combat is fine. Do whatever would allow you to maximize strategy and balance with the lowest amount of the budget. As much as I love Baldur's Gate and Icewind Dale combat, the same type of thing was, in my opinion, done rather poorly in games like KOTOR and NWN and even DAO wasn't great at it. Which probably also means that allowing a party that is large enough for strategy to mean something, and having full control over all party members is essential. And needing control over those party member is just as essential.
As many have stated, voice acting is not important, and can actually detract from immersion. Ignore it completely or keep it to a minimum.
Make a stylized graphical choice that looks awesome but doesn't require technical brilliance (and an absurd amount of money) to achieve. In my opinion, games like Trine 2 and Bastion look better and artistically-speaking leave a more lasting impression than many AAA games. Speaking of graphics, make sure that whatever choices you make, especially concerning the camera, are conducive to the gameplay. There's a reason that isometric is so popular for strategic RPGs.
One difficulty I can see you having vs the Double Fine guys is that RPGs are much more complex games than point-and-click adventures. That means more development time required, and higher cost of development. It's not hard to imagine Double Fine's game coming out within a year. It is hard to imagine an RPG coming out that quickly, which could definitely hurt your chances of getting the funding you're looking for. Consider ways to combat this, such as releasing the games in chapters, and making the reward tiers tied directly to the chapters. i.e. If you contribute $10, you'll get the first chapter, and you can buy the others after they come out. $30, the first three chapters. $50, all chapters. If you do this, make sure you tell us up front how many chapters until the story is complete.