So, wanting a 'native' script is not silly, but necessary.

It's totally unnecessary. Both Cyrillic and Latin serve their purpose very well, Slavic languages look neat when written in either. Both scripts have their own advantages and disadvantages but that doesn't mean all Slavs should write in a totally new system.
Even if črty i rězy was used as a script for Proto-Slavic, it didn't stand the test of time. Soon, it was replaced by another scripts which were far better accustomed to the Slavic nature of our languages.