Is the Google Nexus S capable of reading the exFAT file format? If I backup, reformat the internal memory "disk" of my Google Nexus One (running Android 2.3.4) into the exFAT format (for storage of file sizes over 4GB) and restore the contents, will it spasm and die or will it go on as if nothing had changed?
No.

As reported and commented on by various users, there is no exFAT support built in to Android, so the Nexus S will not read the disk.