When did having options become a bad thing?
Sometimes adding an option that really isn't advantageous causes you to lose actual advantages or causes problems. Such is the case here.
The probability of needing to make a precision long range shot with a snub revolver in a civilian self-defense scenario is astronomically low. Even if you did, you can still get it done virtually as well double action if you know how to properly work a double action trigger. So all you gain by having single action capability is being able to make long range precision shots slightly easier.
However, by gaining the option of single action, you lose...
1. A better double action trigger.
2. a snag free draw
3. the ability to fire from inside a pocket or purse.
4. grip options, specifically any where you take a high grasp on the back of frame. Such holds effectively lower bore axis, allowing for greater control and faster follow up shots.
5. ECQ advantages such as no hammer to be obstructed or blocked during a disarm attempt or close-quarter entanglement.
6. protection against claims you cocked the gun creating a hair as well as no concerns you actually will. If you are practicing firing single action at the range, you very well may cock it under the stress and pressure of a real defense scenario. I witnessed this personally watching my wife panic and go through this during what we thought was an attempted break-in with her model 60. I sold it the next day and got her a 640.
A bodyguard model rendered DAO has many of the same advantages as the centennial although not the same efficiency in ECQ scenarios since there still is a hammer that could be possibly be blocked. Grip options are still limited as well. Plus you have concerns of lint, crud, debris getting down in the action. The only benefit being able to check for high primers and perhaps a slight degree of greater safety during reholstering which aren't much of an added benefit IMO, especially considering having to have the gun worked on to render it DAO plus the DA trigger still won't be as good as the Centennials.