How would it sound if I used a component set low in the doors with a hard dome tweeter and added a set of soft dome tweeters in the pillars/dash (same length to listener)? Would it sound bad using two different dome materials so close to the listener?

If I were to do that (and I'm not necessarily saying I would, nor that it is a totally bad idea either) I would do the hard domes in the a-pillars and soft in the kicks. Reason being is a soft-dome is not as bright (sensitive) in the 10k+ range as a hard dome and is usually more dependant on being on-axis with the listeners ears. Kick panels aimed at the opposite listeners are basically on-axis. Hard domes can work better in an off-axis situation like a-pillars. A tweeter that is in closer proximity but off-axis can be quieter sounding that one longer distance away but on axis.

Hey Sean, totally off topic, but how's your subbox sounding? You got it all broke in and everything?

IMO, you'd probably have too much high freq in the front stage, unless you attenuated the tweeters significantly. If you were going to go with two tweets and wanted to keep everything balanced I'd recommend another mid to go with it. I've seen some well imaged front stages utilizing the apillars, however they also installed a midrange driver there as well. of course it depends a lot on the acoustics of the car too. Another disadvantage would be that there is a large distance between the midwoofer and the tweeter, which will also affect imaging.

Just a thought. Have you considered going with kickpanels?