I use another app that allows me to control the zoom/font size by pinching. It's incredibly convenient, and would be evern more so in Logos, since the Greek, Hebrew, and English fonts don't line up well in size. That is, I set a certain zoom size for English, but that's not my preferred size for Hebrew. So I change it for Hebrew... but then 10 minutes later I'm reading in English again, and would like to change the font size back.
So pinch/zoom for the font would be great.
