Unicode did not encode the construction diagram (or logo) for the Euro,
so all the carping about that is a red herring.
For the Euro, see 20AC at
http://www.unicode.org/charts/PDF/U20A0.pdf
Nevertheless, the construction diagram for the Euro, with it's open
circle, provided some form of starting point for the typographers, and,
as you note, the closest shape they had was the C.
I do expect a similar development for the Turkish Lira, with the
pressure to differentiate the shape from all other known currency
symbols, foremost the British Pound £.
The Lira sign at 20A4 is glyphically an alternate (double stroke) of the
pound sign. Visually it is based on the script form of the letter L,
emphasizing the curved top of the letter shape.As for the pound, you'd
expect existing font renditions for 20A4 to emphasize the same style
elements.
The new logo for the Turkish Lira may also, ultimately, be based on the
letter L, but it emphasizes a vertical stroke and a curved lower leg. As
before with the Euro, the nature of that curve will not be based on the
construction diagram, but the fact that the logo will exist on bank
notes is what will provide the push for people to reject a £ based shape.
Where precisely this will settle will depend on the work of typographes
over the next few weeks, but I'm confident it will result in a shape
that is visually distinct from that for U+20A4, entirely independent of
what Unicode does or doesn't do. The handwritten samples look more like
a letter t, and perhaps that's how the type evolution will go as well.
Remember, none of the shapes for € are based on the letter E or e, so
I'm not betting that basing the glyph for this symbol on L will be the
foregone conclusion.
What you and Andreas are advocating, that is not to add a code point,
would require a wholesale glyph change for U+20A4. All existing fonts
would have to be tweaked to suddenly have shapes based on a L in a
Turkish slipper (that's what the "times-like" example in the proposal
document reminds me of) instead of a script-like shape (based on £).
Such a change would retroactively affect all online documents and would
represent a massive violation of the character code stability policy.
Documents using U+20A4 and written before 2012 need to render the same,
using the same fonts. They should not have to willy-nilly be forced to
"update" the glyph to a shape unrelated to what that character looked
like than and utterly unknown (and you might say, inconceivable) at that
time.
A./