あまたつ - たつ immediately translated in my mind to dragon from too many fantasy games. The あま gets expanded in the description to あまかける, which plugged into online dictionaries becomes 天翔ける, to soar, but あま is a reading of 天. So you could translate あまたつ to "heaven dragon," but you could also leave it as "amatatsu," since using kana makes the meaning more opaque and context reliant. The party might know it is dragon parts, but really just not know how to use it; they just haven't shown us what they know.
Otoha's intro on page 16 is even harder than just being all hiragana. She didn't even type any dakuten, handakuten or prolonged sound marks. Your solution might be the best way to localize it since there are parts that are completely correct, alongside various levels of "misspellings."