Radio Controled Control line.

I've not heard of i/c engines used that way! 
It sounds like a mixture of electric round-the-pole flying, and something else!
I'm trying to envisage a way of mounting a servo on a pole that can rotate, but that means the receiver and battery will also have to rotate, which could be an engineering nightmare!
You would need some form of lever at the top of the pole, with the control line lines running through it, to allow the model to pull the pole around to keep up!
That - in turn, would need a very free-running bearing at the bottom of the pole, and a counter-balance to not only balance the arm, but the tension of the model on the lines!

Getting a standard servo to control the model  - would need a push-rod from the servo to a much larger 180' control horn on the end of the arm, so you could use a fairly small movement (geared down) 'handle' to operate the model, so the load on the actual electronic servo wouldn't be that great - the tensile load would be on the 'handle' just like in regular control-line, where the flyer is hanging on to one end of the wires, via the handle in his hand.

What that tensile load would be is a matter of guesswork, you would need to know the weight and speed of the model.
Don't forget, the smaller the diameter of the circle, (depends on how big your garden/field is) the greater the apparent speed and centrifugal mass the device would have to cope with!
It's an interesting idea, though!

If you get anywhere, let us know if it worked out!

I didn't think of putting the radio in the model either! (duh!) I was thinking of external radio, so ANY model could be 'hung' onto the wires without needing to switch receivers and batteries over.

You would be better having throttle and elevator, so you could limit the speed and duration of the flights!

Cheap radio - plenty on e-bay - and for a tethered model, it cannot fly away if it proves faulty. (If it is any good, why is it on sale cheap?)
Books on r/c - I don't think there are any, really. There's not a lot to know, just plug the bits in and switch on! (battery - switch - receiver - servos) With modern 2.4 Gig kit, there's no messing about with crystals and frequency control, all you need to pay attention to is charging the batteries in the transmitter and for the receiver.

Or as suggested, join a disabled-friendly club - for example the one I'm at, we have a hard surface right up to the cabin, and a hard (flagged) footpath from the cabin to the flying area.
You don't say where in the country you are, so probably our club is too far from you - haltonmfc.co.uk/
That's me under the sunbrella!

Learning to fly r/c with a Spitfire or a Mustang (or any warbird) is rather like going for your first ever driving lesson in a Formula 1 car!  

You might be intrigued to know that one of our founder members was called Phil Wood, nicknamed polyfilla. Regrettably he is no longer with us - he's gone to the big flying club in the sky.