Impossible because the decision was already made by Turkish encodings, which made Unicode to pick only one option (round-trip compatibility with legacy encodings) out of possible trade-offs.
This isn't honored; we have many Unicode code points that look identical by definition and differ only in their secret semantics, but all of those points are in violation of the principles of Unicode. The Turkish 'i' is doing the right thing.
E.g. Cyrillic "а" looks the same as Latin "a" most of the time, they both are distant descendants of the Phoenician 𐤀, but they are two different letters now. I'm very glad they have different code points, it would be a nightmare otherwise.
Having distinct code points for Latin capital letter A, Greek capital letter A, and Cyrillic capital letter A is the reverse, separate code points for glyphs that are identical by definition. That's also a mistake.
(Although it might be required by Unicode's other principle of being fully compatible with a wide variety of older encodings. There are many characters, like 囍, that don't qualify to have a code point, but that have one anyway because they're present in an encoding that Unicode commits to represent.)
Why do we then have lots of invisible characters that are intended essentially as semantic markers (eg, zero-width space)?
But the which strings are encodable in legacy codepage depends on what we define as encodable! If we had separate codepoint for "turkish small letter i" then we could have simply defined that "latin small letter i" is not encodable in legacy turkish codepage, same way that "cyrillic small letter a" is not encodable to turkish legacy codepage. "turkish small letter i" and "latin small letter i" would be just another normal homoglyph pair, same as "cyrillic small letter a" and "latin small letter a".