Is spelling with numbers a viable option to remember tones?
For natives, I think the learning path would be:


  Speaking/talking -> Pinyin -> Characters


For example, when we see a word like 你好，we would think about what it's pronounced like and then figure out what tone should apply to them. 

I think this could be a good way for non-natives to remember tones for characters as well. 

With the way(lao3shi1) OP suggested, you have to remember tones by rote, and it's very easy to forget, and you might not apply those tones well when you speak, because you have to think about the tones all the time while you are speaking. 

Hope this could help.