I already made a few modern fonts, check my gallery and this site: [link] Semicolons, colons, and exclamation points are unnecessary for phonetic-syllabic types of languages and I advise not to "invent", re-invent, or add new symbols or characters to the original set unless it is truly necessary. In modern writing, if you want to express these types of pause and tonal/pitch change, you can use the modern symbols along with the ancient script (such method has been adopted with modern Japanese & Chinese writing). There is no reason not to use a modern exclamation point, hyphen, colon, or semicolon when writing baybayin in a modern composition. I think some of the purists who are too strict with the rules contribute to the decline of the script's use. The only punctuation marks I am wary about are the ones that may be confused with the kudlit such as apostrophes and quotes.