Divebomb makes a good point, this game hasn't got a huge following.
Infact (as you can see from the comments on the video) alot of people instantly dismiss this as "another wolfenstein clone" which, aside from being utterly stupid and annoying as hell to see posted for every vid, is also the reason why this game hasn't been checked out by the majority of the gaming world.
You should look at this as more of a re-vamped version to (hopefully) get more people interested. The addition of more vehicles might actually stop idiots from claiming this to be a rip off and instead actually play it.
Perhaps sometime in the future we could see a true add-on for NecroVisioN - But for now, any new levels/baddies/weapons/features are much appreciated.
Oh and as for the comments about taking up disk space - I didn't think this was even an issue anymore, hard drive prices have been dropping steadily for a long time. 8gb is nothing when most systems these days have well over 2TB of space.
I've got 4.5 myself, and just recently bought another 2TB for about $250 AU. If you are that concerned with having to install many of the same files again, i'd suggest you get another drive to save future hassles too.
Games are just going to keep getting bigger and bigger. Soon enough we'll need 20-50GB of HD space just for a basic game. Best to get ahead of the trend now rather than later.