Hi Rob,
As a keen club carpet racer and a basher (thats car speak for mucking about non competetive driving) I can make one or two suggestions.
Racers are moving toward 2.4Ghz so the cheap 2.4 stick sets 2/3 chanel are proving a hit.
Personaly I am on the notification list for the Frsky 4ch receivers. When they are in I will be grabbing a Fut Module and a pair of 4ch RX.
Small receivers are the key for cars. We don't need 8 ch receivers

I have posted a sugestion on the normal thread for switches to plug into a Rx to switch on stuff.
Crawling is getting big, so switches will be great for spotlights etc.
You may want to look out for cool gadgets like winches. But I don't know how many you would be able to shift.
Stuff like that is available but usualy on US import so it may be the restriced availability and cost that is slowing the uptake.
You already do some car or car useable stuff so perhaps some cross reference pages on your already good site. Esp BL motors as they are in demand.
Main thing is to get the Cod out into the car community which might just be a few carefully placed posts on RCracechat or similar.
Thats a start. Now you have my brain engaged I may think of other stuff.
Kevin