I think the best thing to do would be to create a small function that let's you change to whatever text you like. Then you can call the function on mouse over / out of objects, characters etc. That way, you could have full control as needed. Would be a bit of work on your part though.definition script...
to use: create execute a script action, containing...
game:setValue(VGameActionTextFont, getObject("Fonts[" .. n .. "]"))
... simple enough, no?
Or you could do it at beginning of the scene as you said - which will probably be more ideal if everything in that scene is to use the same action text font. Just make sure you set it back to the default text in an at end of scene action, if required.