The crossovers in your paradigms are designed specifically for the drivers that are in them. Changing out the drivers would most likely have a very negative effect. Furthermore, the speaker itself (driver layout, etc) is designed around the drivers in use, so altering the characteristics of the tweeter would make it sound wonky.
If you like the soft dome sound, I suggest you check out the PC-Series from Phase Tech. Their PC 3.1 II speakers are like large bookshelves, but have the bass performance of many floorstanding speakers. They list at $1200/pr. The full-size floorstanding speakers, the PC 9.1s, are also awesome (I believe you've read my review) and have an MSRP of $2000/pr. The technology in the PC series is really pretty cool. The woofers are actually solid, low-density foam with a flat front.