I find your description of your DIY system very interesting. I too really like the AER BD series of wide-range drivers and I really like the idea of using them as a wide-range midrange driver. When the vast majority of the lower midrange to high frequencies are covered by a smooth driver like the AER drivers, the sound is quite special.
I like horn-based systems that also utilize a compression driver/horn to cover a similarly large part of the midrange, with woofers coming in quite low and a tweeter on top for just the very highest frequencies. This can be done without using digital time delay for the drivers and it still sounds good.
I have a system with a compression driver/horn midrange (Western Electric 713b driver KS12025 horn), twin 12" woofers in a Jensen/Onken cabinet) and Fostex bullet tweeters like yours on top. The 713b driver is my favorite compression driver, but, it does have the disadvantage of not going very low, so mine is crossed over at 700hz. A local shop, Deja Vu Audio (Tyson's Corner VA), makes a lot of horn-based custom systems, and with the really big horns; they crossover the compression driver as low as 150 hz, with the tweeter coming in at a 8,000 hz or higher. These horn systems, as well as systems utilizing wide-band cone midrange drivers (like yours) are so lifelike, vivid, and harmonically saturated, unlike many more conventional systems.