I don't mind the prefixed punctuation at all and don't think it hurts readability in the slightest.

Your inexplicable decision to capitalize the final letters is awful though, and definitely makes it less readable.

lol yeah I guess it depends on the length of the sentence and the context. Context is usually pretty clear for questions, and maybe exclamations are typically short enough that the '!' is already visible anyways. Definitely wasn't considering periods and commas in that list.

.I feel like this analogy doesn’t entirely work because you always know where the question starts, as that’s where the sentence startS.

Not always. For example (translated):

And you, ¿how are you?

Ngl in my head I read this as "I. . . feel like"