The only upgrades are those that were available historically. The Type II didn't get too many of those.
As for the game itself, there isn't much development going on. More people are still making mods for SH3 than SH4. Operation Monsun could use some upgrading, but mostly what's missing are the little immersion mods that could be transferred from SH3. For details check out this thread.
http://www.subsim.com/radioroom/showthread.php?t=181139