Variable Fillable Text Field Size

A question which I think has an easy answer, but not the one I want to hear!

I'm creating a fillable form, of which the answers inputted to any given box can be hugely variable in size. Rather than estimating the size of an answer and having the text auto shrink to fit the field if it goes over, is there a way to have the text field expand/increase in size if the input is too big for the size?
The only options I can seem to find is multi line/auto size text and scroll text. Unfortunately, the input could be large enough to make these somewhat obsolete - the answers can vary from a line to several paragraphs.