Do you have a particular dimmer in mind? It would be real helpful if we knew what specific dimmer it was and why you need it here.
The Arduino can implement any dimming you need and can be programmed to take the dimming control from a variety of sources, such as a simple potentiometer. Perhaps the dimmer is not needed at all.
It looks to me that you want to use the Arduino to convert between some PWM signal and a 0V-5V variable voltage and possibly do some distribution (send output to multiple LED power supplies). Is this more or less correct?
Sorry if this sounds patronizing, but it would be great if we could get an explanation without all the jargon. It is clear that you may not understand a lot of this yourself, so if you told us what input/action you want and what output/response you need in plain terms it might help a lot. For example, "I want to be able to turn a knob and have the LEDs get brighter or dimmer depending on which direction I turn the knob" or something that more aptly describes what you are after.
Also, the Arduino cannot give you analog out. The best it can do is PWM, which would have to be filtered and buffered to give you a real analog signal.