Your idea could work. Since angels are known for their aggressiveness, there really is a strong tendency for them to hurt each other, but it shouldn't always be the case. You can always observe their behavior in about 3 days and then if you feel that they're being too aggressive with each other, then ya, move the other angel away. What angel will you be getting? There are lots of them. Here, maybe this link can give you an idea of what to get.
Pterophyllum scalare (Angelfish)
Goodluck!