The Evo LTE *DOES* have a removable battery. But it requires a few minutes and removing a two screws. It is not a "quick swap" battery, like in the Evo 3D and Evo 4G, however.
You can't put a physically larger battery it in, but perhaps a denser one (if they are made- I have only seen the direct replacement, which is the same energy density/capacity as stock... and was surprisingly not expensive).
The One X and One both have essentially NON-removable batteries, because the battery is sandwiched between the display and circuit boards, making them essentially non-serviceable. When the battery wears out or fails, those models are essentially trashed.