Hello Martin and John,
There is such a diversity of model boating on here that you could include subjects across the whole range. Organise it into four main topics ie Scale, Sail, Power boats and Submarines. Then subdivide if required.
Just for starters you could include setting yacht sails for optimum performance, setting up and tuning different types of I C engines, there have been some good suggestions this year on reproducing hull plating on warships (John

), I personally would like something on hull construction as I am about to tackle bread and butter construction for the first time. Advice on fibreglass has been discussed a few times and would make a good how to.
And for sailing/operating how about a guide to tug towing and regatta course sailing in terms of rules and techniques. It is something that appeals to me but I wouldn't want to just turn up and have a go without first knowing a a bit about it so I didn't make a fool of myself

.
Clive :)