Rather than attempting to read the entire file into memory, the vi applet could load the file in chunks.  This could be the default behavior or an option. This would allow viewing/editing arbitrarily large files while using a fixed amount of memory.

My primary use case is dealing with large log files after a crash. I want to be able to boot my forensic tool on a memory-constrained box, search for and cut-n-paste relevant log file entries.