Guys, all pi$$taking aside, I think this idea has some merit.....
I subscribe to a few mags (not all top-shelf) and one of the best in terms of understanding of its readership and ability to deliver something every month that's informative, fun and bang up-to-date, without taking itself at all seriously, is the VW T4&5 magazine which was started just a couple of years ago by two serious 'camper dubbers' (in a market allegedly already catered for) following a canvassing of opinion amongst the membership of the T4 and T5 online forums, circa 40k members.
The Editor and Deputy Editor still have full-time jobs but they've partnered very successfully with a small, specialist, publishing house who deal with design, subscriptions, printing, ad sales, etc.
The administrators of this site will have the detailed figures regarding membership numbers, active members, etc, etc but as someone new to ribbing and thirsty for information, there appears ampple room in the market for a RIB/SIB magazine?
Whether the market's big enough is another question best answered by someone in the know....