If that kind of thing bothers you... I wonder what you think about GAZ3 (Glantri). It is very fun and imaginative, but crazy and disjointed.
After analyzing what I got, and giving it some thought, I think there's two ways you can go about DMing in this setting.
A) The "Known World" approach, that is, taking what is published up to B10... or maybe up to GAZ1, which gives you a low-fantasy setting with clear dark ages feel; Karameikos with its slavic-inspired dark woods, Thyatis as a byzantine-like sea-empire colonizing Karameikos, and a few islands to the far south is all it covered. From anything published after that, you'll need to use caution, and take only what is consistent with this base setup.
B) The "Mystara" approach in which everything printed goes. Flying ships and islands, and anachronism up to 19th century, gnomes building giant robots, connections to our own world (scottish lich with a kilt, french nobles coming from actual France, etc)
I will certainly go with A) because I'll start my campaign around B10. I can imagine running one day a very fun, humorous and silly hi-fantasy game playing Glantri as written, but it's gonna destroy any other type of game IMHO. My Glantri will be a mediterranean-inspired land of magic city-states, yes, but I'll stay away from the gondolas with mounted magic-missile cannons and the atomic-energy devices from the future. Alphatia as described in Dawn of Emperors sometimes crosses lines as well, but nowhere as much and I can easily accomodate it to my needs. Flying ships and cities? Yes, but over centuries of decadence they have lost the knowledge to make more of them, which would make sense given the Alphatian lore. That makes plausible their defeat in the war with Thyatis, too.