curious question
 

If you wanted to replace your tensioner or roller but did not have the cam locking tool, an idea.

Since the tool keeps both cams on the same tooth on the belt if you were to zip tie the belts on each cam since you are not replacing the belt it seems as if it would work.

On the same subject I did not see any mention in the bentley about putting any type of thread locker on either the idler or tensioner hex bolts even though it would seem like a good idea.

At only 33lb torque if the tensioner bolt was to get loose enough for the tensioner to turn the belt could get enough slack to come off the sprockets.
Likewise the idler is less at 18lb.

Not really.
 

Depends on what your definition of "it would work" is. The car would run, and timing would not be any worse off than it was before, but to do the job right you should free the sprockets even time you are in there. Cam timing is infinitely adjustable; if at all possible, it should be adjusted every time you touch the belt.

what I mean is
 

if you were not going to replace the belt so you wanted the upper portion cam wise to stay exactly where it is but wanted to replace the tensioner, roller or just a bolt then locking (ziptie to cam) the belt, replace the lower parts, tension it back up then remove the zip ties.
If the belt stays on the cams and crank without moving the timing should remain as it was.

Just a backwoods way of not doing the entire job if you only need to replace one item or so.

Yeah, I got that.
 

To quote myself:
"timing would not be any worse off than it was before"

...as you say.

I was curious because
 

On my mom's A6 the guy she bought it from replaced the timing belt and WP but nothing else which makes me worry. Seeing my own parts recently after 60K I can say in my case the idler had some grease around the edges but otherwise was spinning without issue.
The tensioner though was dry and fairly stiff to turn so I'd just replace that as I am sure if it was done before if ever it must be wasted.
The A6 is pie with the front clearance and easy off cover plate without a need to even remove the fans.
Downfall is the hood is a bit longer and I rather like the compact B4 look personally.