You actually might be interested in a brand new feature only available on the latest Sketch Beta (Sketch 58) as of today, September 1st.
Here's the link to that beta: https://www.sketch.com/beta/
As you can see :
Introducing Smart Layout With Smart Layout, we’re making Symbols more powerful and supercharging your workflow when it comes to using them in your designs. With it, you can set a direction for Symbols to resize when you change their overrides, while keeping the spacing between different layers in that Symbol consistent.
That allows you to create something like this : https://gfycat.com/fr/likablescalyjay (I'm sorry it's not embedded, but it seems imgur does not want to upload the gif version of it...)
High quality version : https://giant.gfycat.com/LikableScalyJay.webm
So, to create a symbol that will resize correctly with some text inside, you now have new options called
Smart Layout either when creating the symbol or after thanks to its settings.
You can then override its text and... tadaa! It will resize automatically.
I know it's not the best answer since Sketch 58 is still in Beta but you can download it and use it as a separate application.