Unified Zireen Romanization

I'm working on a unified system of romanization for all Zireen languages,
to minimize confusion when dealing with more than one language. I have a
number of clearly incompatible goals.

* Use only characters found in commonly available fonts, like Times New
Roman and Courier New.

* Have distinct letters for upper and lower case.

* Have distinct letters for all sounds that are distinct in Zireen
languages.

I run into problems pretty quickly. The retroflex sounds can't use the IPA
symbols, since most of them don't have upper case forms, and none of them
are included in typical fonts. They could use the "dot below", but this
appears to the left of the character in Times New Roman, and all diacritics
are spaced after the character in Courier New. So I think I'll use the r-
prefix for retroflex sounds.

Another problem is the glottal stop. I could arbitrarily pick upper and
lower case forms (e.g., ? and 7), but a search wouldn't recognize these as
the same character.

I can use a few Greek or Cyrillic letters, but only if both the upper and
lower case forms appear distinct from the Latin letters. So I can't use
Greek beta, for instance, since the upper case looks just like a B. So far
I've decided to use theta and delta for dental stops, which are distinct
from alveolar stops in Jaradh.

If I allow any character that's available in Thryomanes, I have a lot more
options; I could use dot below for retroflex sounds, and there are even a
few IPA vowels that have uppercase equivalents. I also have a wider range
of diacritics I could use, but the ones that go above the letters can only
be used on the lowercase letters unless there's a precomposed character.
The Times New Roman diacritics float way up above the letter, so they can
be combined with both upper and lower case letters, but I don't really like
the way they look above the lowercase letters.