Agreed, but there could be a few speedbumps if we want to get there.
It can be extremely easy to mod the NavyField client where you can enter an offline mode and setup custom battles. Emphasis on the word "can".
If it were offline, it would have to use bots, and those of us who have played missions know how good the bots are at playing...
I doubt this would cause more crashing or adversely affect the reliability of the client.
The biggest problem I can think of at this point is, what about user profiles? One of the major things about an online game is a retrievable profile you can fetch from anywhere with an internet connection, and the idea is that you use this profile. If you're offline and can't access your hard work, then what profile can you use?
You could import your own profile and save it to a directory which the offline client accesses... but I get the feeling that somebody is going to get somebody else's profile for the sake of ships. That may be a bad thing, but then again it might not.
You could start like they were a new player, with only the level 1 starter crew... but that's not fun.
You could be required to connect online in a session before being able to revert to an offline status, which would allow it to grab your profile independantly from the NFNA servers, but what if you can't connect to the NFNA servers in the first place? (A very real possibility given the fact that the server has been crapping out over the past month or so)
However, even if you have to connect to Enterprise in the first place, I think that an offline mode would in this case still be useful. If you want to play NavyField but you're lagging so much (big surprise) that you can't play online effectively, just revert offline. Server going down in 3 minutes? Revert offline, and once the server is back up then revert online again. I don't think that they would let you gain credits/points/exp in an offline state, since you could be hacking without any anti-hacking protection - but if they do allow it, it would be nice. Even if it was at, say, a 50% penalty. Great idea, hope it moves forward!