The problem is that is the start of the dependencies, not the end. :) If we want to ship custom libc, we have to build also every other library which is needed for the game.
Normally, these libraries included into the system. But they are compiled with the system's libc. In our situation, it would be some X server libraries too. I'm guessing how much space it would be taken. If you want to see, what need to be rebuilt, you will need to unpack the game to get executable and do “ldd” command on it. It should give a full list what is needed.