Seems sensible to me, but unless your rudder falls off completely, it is more likely to get stuck at an angle, and therefore you could end up going around in circles! This is what happened to us on the River Humber when we caught a large barge sized rope around the prop, which not only stopped the engine dead, but locked the rudder solid as well!
I also find that most boats will have a tendency to driff off to the side anyway, even out of gear! On a canal I don't suppose it's really a problem, but a useful trick on a wide river I guess.
If I let go of my tiller on Shoestring, she always turns to the left. My other boat is a little better behaved, but underpower will usually eventually pull either to the left, or the right depending on how close the tiller is to centre. I suspect the rudder balance is wrong, or perhaps the rake on the shaft.
In reverse Shoestring's stern pulls to the left, so I try to get on the left side of wide locks where possible. I'll have to give it go when actually travelling forwards, and see if it will pull the rest of the boat round.
GU Boats like the Narrow Boat Trust's Nuneaton (a large Northwich) were designed to pull to the left in reverse, so that they could put the butty on the starboard (right) side of the motor. This gave the motor the deepest part of the canal when passing other boats when brested up. Unfortunately, since they replaced the original engine, it now pulls to the right causing allsorts of annoyance!