such large USB sticks you have, must be making up for something else ;)
Iv got a 64MB one, had it for years, iv got Scar, and GCC and for java, i have this little app called SIDE, its about 1MB and it can compile source code and has a syntax highlighter and all that, but you need JRE on that computer to run it, the program is quite buggy, but its open source and iv fixed some of the bugs on my copy, you kind of have to learn how to use it, workaround the bugs,
SIDE's thread on moparisthebest's forumsperhaps if one day i get another USB drive, ill look into getting a portable JVM, or just the "offical" hotspot VM
you could use a batch file to set those path variables i guess, i heard of someone who did that in his univercity years