It'd be interesting, but Q3 is kind of like, dead, dude.

The main thing is you'd need not only a group of talented artists to revive it, but people who're interested in actually taking their time to work on something without any payoff. (say there would be one all you want, but c'mon, honestly - the mod scene for this game in general is gone) And those're hard to come by.
I personally say at this point coding is not the issue, but animations, models, and maps. The skinning of the current models has made everyone I've shown it to gag (my entire crew could not stand filming in this mod at one point and seemed to stay away from it) and the animations, while good, are nothing spectacular and require a great deal of work and reworking. (particularly since to make things work proper, you're gonna need the ponchos to flow realistically - that's a pain in the ass to animate)
As well, the sound work. C'mon, I know it's going for authentic spaghetti western feel, but you don't have to keep it that friggin' low-quality.
Would this be worth it?
Perhaps.
But to be honest, I'd prefer to see a team pool their resources into doing something for the new generation like Doom 3 and HL2 that has the Western feel. Not that I feel it'll be done well.

So, there, another opinion for ya.