I was browsing through Forgotten Trek recently and came across this interesting concept. Greg Jein designed this concept art for an enemy station that was to be used in the first episode of the final season, and ultimately most of it wasn't used for cost purposes (among others). Greg was filling in for John Eaves at the time. Link (Eaves' blog)
I dunno, that seems way to seamless how it incorporates both Jem'Hadar and Cardassian designs. I'd see the Dominion deliberately building only Jem'Hadar facilities and "phasing out" the obsolete client state's designs along with their military and any threat. This was also demonstrated with how Weyoun was clearly letting the Cardassians soak up the casualties during the war.