Operating accessories and other structures at curves... ever done?

You are right about the curves. Often you must be at least a few inches into the straight to account for overhang of engines and cars as well. 

Do you have any pictures to see what you are working with? Which accessories are you placing?

one tip would be adding ‘dummy tracks’ that are only there to serve an accessory. That way you could operate the accessory, but you would have to pick the car up with your hand to add it to the main layout tracks. 

I have forgotten about the overhang issue.  Guess that would likely preclude any accessory that needs to get close to the track to operate, such as a milk platform, which has a small footprint.  Also UCS or uncouplers aren't on curve sections either.

I usually place trackside operating accessories at curved sections.  Things like the Oil Rig, Crossing gates, Switch Tower, etc.  basically, anything that does not directly interact with the train.

What Dan said!

How about an operating water tower?  i have one on the inside of a curve, but outside could work too.

The only operating accessory that I have placed on the outside of an O72 curve is a #97 coal loader, but its not hooked up...I just have it there looking pretty. Other than that, I have non-operating structures on the outside of other curves, such as depots, stores and an Irish pub. My largest loco is a JLC Challenger, which swings out quite a bit, even on O72, but that has been taken into consideration.

Water tower. 

Accessories with reach i suppose could work very well.  I have one area where two O54 curves meet at a Ross O54 switch and above which an elevated section of O72 crosses.  If I put a 282 gantry on blocks I may be able to access all three tracks for load transfers and such.  Picture below.

Where tracks converge at a switch is there anything that is typically placed there... like dwarf signals?  

Kirk R

Tunnel