@Ubbergeek
Yes, you're right. Me too I overreacted the other day, and now I know it was because I jumped to conclusion too easily. There's always a way to make D&D do what you want to do.
@ OP
-There will be rules at the end of the Monster Manual to convert the Gnome as PC.
-There are going to be Giants in the Monster Manual you could easily adapt a Frost Giant.
-If you want you can remove the Tiefling race from your campaign world.
It's an art (adjusting a game), and it's not easy to master, but it will be easier for you if you don't even give it a shot. But it's your call, and I respect whatever your decision will be.