Sure, and in a Japanese song, "sensei" can yield four beats or notes SE/N/SE/I.
But spelling out and singing aren't normal speech. Spelling/singing can break apart diphthongs, like NAI becomes NA-I.
生 is not written with い due to the /e:/ having a different sound from that one in from おねえさん. It does not (when you aren't spelling). It is written the way it is for ancient historic reasons.
> Similarly, the OU in 東京 (toukyou) and the OO in 大きな (ookina) are different
No, they are't.
> I hope this helps.
こう言うバカな戯言は少しも誰にも役に立つはずないんだぜ。
We are talking about writing/spelling, aren't we?
Why would you want to confuse the hell out of those learning Japanese by spelling せんせい (sensei) using an E with a macron, a la "sensē," when that is not at all how you spell it or type in phonetically in an IME? Having a one-to-one romanization for each Hiragana phonetic is far more logical for learners, who are essentially the target of romanized Japanese, than creating a Hooked on Phonics version that is completely disconnected from writing reality.
I also think your comment, written in Japanese, saying, "This stupid nonsense isn't going to be of any use to anyone," is both ignorant and uncalled for.