Even if some programmers would say "yes!, maybe" I would definately say "no" when it comes to the Fallout 2 engine. There where multiplayer "hacks" for games like GTA3 and Vice City. They're unstable till today because they access old multiplayer rountines that are already in the game and try to get them back 2 work. But as long as you don't have the sourcecode this will not be a good idea.
However, there is a Fallout port, called IanOut, which aim is to get Multiplayer working with a Fallout-like engine, too. Check out this post:
http://www.nma-fallout.com/forum/viewtopic.php?t=2183 and read through the IanOut forums here. The code for multiplayer is already in the current build, but the build isn't public and I think it will be deactivated for the release because it's very buggy ATM
So you can:
1. Wait for IanOut with multiplayer; this will also ease the modding a lot, because IanOut isn't limited like the Fallout engine. It support supports resolutions until 1280 x 960 (1280 x 1024 for TFT's) and .ogg sounds for example; and the filenames didn't have the old 8.3 DOS restrictions so long filenames are supported
2. You choose another engine for your game. It don't know how far the guys with the modified Jagged Alliance 2 engine got, but I think they will support multiplayer, too. Maybe I'm biased but I'm quite sure that you'll see multiplayer on our engine earlier. The problem is that their engine supports a lot of combat stuff but bartering and dialog trees aren't supported and had to be coded by you (them, if they want to use it) so it would be easier to wait for IanOut
3. You drop the idea with the multiplayer support and take the Fallout 2 engine. Maybe this is the best start because you can start NOW to work on your mod. IanOut will have converters later; so if you think IanOut is good for your mod you can convert it later anyway.
Hope this helps you
