macOS Text Replacement

I'm a fan of this web comic called Homestuck and from that I what to be able to role play with my friends. MSPARP is great but I'd like to be able to us automatic letter replacement with Skype. I was wondering if there was a way for me to change the keyboard in a way that, for example, B and b would be replaced with 6 and o and O would be replaced with 9, so if I typed Bread oven baking bones it would instead print out: 6read 9ven 6aking 69nes. I have already tried Apple's text replacement, and it only works with things separated. It would be nice if a daemon could be made with a tab in the menu to change it. I was thinking about maybe making it a language and being able to select it in the menu bar as well if that's possible. Thanks for all the help you can contribute!