You know what they say about opinions, but...

Sure. You can safely replace the 2-sided mirror with a grid/star/cross 1-sided one...as long as you practice and can use it if you need it. Muscle memory can be a pain as well as a benefit...I've caught myself using outdated techniques on modern equipment because I trained on the old stuff to the point where I didn't have to think. Guess I'm getting lazy in 'old age' and don't invest the time on new gear the way I used to on old stuff!