Removal of unused pads?
This is not a standard practice, and should be avoided.

First: Along with providing electrical connectivity, pins also mechanically anchor a chip to the board. Each pad that's removed increases the stress on the remaining pins, which will increase the risk of the chip detaching from the board.

Second: All of the remaining pins have nothing but soldermask between them and a trace underneath them which they aren't supposed to be connected to. Soldermask is not very thick, and it's not very durable either. If the mask is breached -- from a pin vibrating against it, for instance! -- the pin may become intermittently connected to something it wasn't supposed to be.