While still staying true to the OPs vision of having a club that was cheap, and pretty easy-going. I agree with those things, but I think you are right, you have to sort of have a vision statement of some sort or it just becomes a bunch of people hanging out. That's cool with me too!
If I had a vote, I would vote Jeeps only, because that is what we are all interested in With that, it becomes at least a little bit exclusive.
There are probably a few things that would need to be done that aren't costly, but they set the ground rules for what lies ahead.
The only drawback to being completely loosely structured is that it becomes a group of people that just hang out, and slowly it could turn into just a group of people who hang out a couple times a year if that.
I am not speaking pro or con on either of these two set ups at all. I am sure we are all busy and don't have time to run a comprehensive club right now.
I for one can volunteer some time on whatever needs to be done. God knows, I waste a lot of time on JF reading much less important threads!