IIRC linguists (like, actual academic researchers) prefer to “break up” kana and analyze the consonant and vowel separately when dealing with conjugations. Treating kana as indivisible units is AFAIK only really a thing in Japanese linguistics historically done in Japan. All this to say, I’m pretty sure this “just change the vowel” approach is perfectly fine from a theoretical perspective (and as a fellow learner, also very aesthetically satisfying :-) )