This would be a great accessibility feature! Unfortunately, due to the way the screens are composed, changing the font size dynamically is not a simple switch. It would be a huge undertaking. I'd love to do it! But I just don't have the time or means right now.
However, there is a built-in engine feature that lets you override font type and size. In-game, press shift + A to open the accessibility menu and you can mess around with the text size there. Just be aware that the game wasn't designed for that, so it will push some text out of alignment, and the effect will be worse the larger the font size.
Hope that at least helps a little!