Opus handles font size in dialogs very neatly. If the size is increased all aspects of the dialog are adjusted accordingly so there is no need for the host script to do anything else. The default font is 8pt which can be a bit challenging depending on your eyesight. Currently the the only way to increase the font size is to hard code it in SCRIPT RESOURCES. It would be nice to have a run time option to load the dialog with a user specified font size, something along the lines of dlg.fontsize=9 specified before dlg.create.
You can set the font size when defining/editing the dialog:
Why would you want to change it at runtime?
User A may have no problem with a font size of 8pt whereas user B would be more comfortable with a larger font. It would be nice to offer a choice by means of a run time parameter or script option. It's possible to do this already but it requires the script author to duplicate the dialog definition, identical in all respects except for the font size and dialog name.
Probably as easy for them to edit the resource as it is to add arguments to a button. But why not just use 9pt by default? I don't think anyone minds 9pt dialogs (8 and 9pt are so similar in size) so the option of 8pt seems redundant, unless I'm missing something.