I think you could divide it up into a number of areas, you'd also need a write-in section to keep in contact with the public.
All-grain and extract could be separated, but then again when doing recipes (probably 1-3 a month), you could do a Can and sugar + partial grain + all-grain to cater for all three brewers. Reviews can be 3-4 per month, covering equipment, a product (yeast) and a kit. I like the way Oliver and Geoff do things (www.homebrewandbeer.com), with some reviews and recipes, stuff like that. You should also add an article or two, including maybe fermentation (temperatures, secondary fermentation, etc), kegging, aging, water chemistry, etc. If you split the magazine into all grain and extract, you could whack half a page worth of text (which would be repeated each month) for example "For the brewer who likes to do things from scratch... this is not for amateurs..." etc and I think you have a lot of potential for articles.
If you can, although I don't know how sustainable it is, you could do the interview thing, a site tour article, things like that.
I hope you end up doing this.